在Cocoa中生成一个随机的字母数字字符串

时间:2022-11-24 21:40:54

I want to call a method, pass it the length and have it generate a random alphanumeric string.

我想调用一个方法,传递它的长度并让它生成一个随机的字母数字字符串。

Are there any utility libraries out there that may have a bunch of these types of functions?

是否有一些实用程序库可以包含这些类型的函数?

20 个解决方案

#1


302  

Here's a quick and dirty implementation. Hasn't been tested.

这里有一个快速而肮脏的实现。还没有测试。

NSString *letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

-(NSString *) randomStringWithLength: (int) len {

    NSMutableString *randomString = [NSMutableString stringWithCapacity: len];

    for (int i=0; i<len; i++) {
         [randomString appendFormat: @"%C", [letters characterAtIndex: arc4random_uniform([letters length])]];
    }

    return randomString;
}

#2


92  

Not exactly what you ask, but still useful:

不完全是你问的,但仍然有用:

[[NSProcessInfo processInfo] globallyUniqueString]

Sample output:

样例输出:

450FEA63-2286-4B49-8ACC-9822C7D4356B-1376-00000239A4AC4FD5

#3


66  

NSString *alphabet  = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXZY0123456789";
NSMutableString *s = [NSMutableString stringWithCapacity:20];
for (NSUInteger i = 0U; i < 20; i++) {
    u_int32_t r = arc4random() % [alphabet length];
    unichar c = [alphabet characterAtIndex:r];
    [s appendFormat:@"%C", c];
}

#4


40  

Surely you can make this shorter:

当然你可以把它缩短:

+(NSString*)generateRandomString:(int)num {
    NSMutableString* string = [NSMutableString stringWithCapacity:num];
    for (int i = 0; i < num; i++) {
        [string appendFormat:@"%C", (unichar)('a' + arc4random_uniform(26))];
    }
    return string;
}

#5


23  

A category version of Jeff B's answer.

杰夫B答案的一个分类版本。

NSString+Random.h

NSString + Random.h

#import <Foundation/Foundation.h>

@interface NSString (Random)

+ (NSString *)randomAlphanumericStringWithLength:(NSInteger)length;

@end

NSString+Random.m

NSString + Random.m

#import "NSString+Random.h"

 @implementation NSString (Random)

+ (NSString *)randomAlphanumericStringWithLength:(NSInteger)length
{ 
    NSString *letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    NSMutableString *randomString = [NSMutableString stringWithCapacity:length];

    for (int i = 0; i < length; i++) {
        [randomString appendFormat:@"%C", [letters characterAtIndex:arc4random() % [letters length]]];
    }

    return randomString;
}

@end

#6


19  

If you're willing to limit yourself to hex characters only, then the simplest option is to generate a UUID:

如果您愿意只使用十六进制字符,那么最简单的选择就是生成UUID:

NSString *uuid = [NSUUID UUID].UUIDString;

Example output: 16E3DF0B-87B3-4162-A1A1-E03DB2F59654.

示例输出:16 e3df0b - 87 - b3 - 4162 - a1a1 e03db2f59654。

If you want a smaller random string then you can grab just the first 8 characters.

如果你想要一个更小的随机字符串,你可以只抓取前8个字符。

It's a version 4 UUID which means the first character in the 3rd and 4th group is not random (they will always be 4 and one of 8, 9, A or B).

它是一个版本4 UUID,意思是第三和第四组中的第一个字符不是随机的(它们总是4和8、9、a或B中的一个)。

Every other character in the string is fully random and you can generate millions of UUIDs every second for hundreds of years without much risk of the same UUID being generated twice.

字符串中的所有其他字符都是完全随机的,您可以在数百年的时间内每秒生成数百万个UUID,而不会产生两次相同的UUID。

#7


6  

You could also just generate a UUID. While not truly random, they are complex and unique which makes them appear random for most uses. Generate one as a string and then take a range of characters equal to the passed length.

还可以生成UUID。虽然不是真正的随机,但它们是复杂和独特的,这使它们在大多数情况下显得随机。生成一个字符串,然后取等于传递长度的字符范围。

#8


4  

Here's a different way to tackle it. Instead of using a prepared string of characters, you can cast between integers and characters, and generate a dynamic list of characters to select. It's pretty lean and fast, but has a bit more code.

这里有一种不同的解决方法。您可以在整数和字符之间强制转换,并生成要选择的动态字符列表,而不是使用准备好的字符字符串。它非常紧凑和快速,但是有更多的代码。

int charNumStart = (int) '0';
int charNumEnd = (int) '9';
int charCapitalStart = (int) 'A';
int charCapitalEnd = (int) 'Z';
int charLowerStart = (int) 'a';
int charLowerEnd = (int) 'z';

int amountOfChars = (charNumEnd - charNumStart) + (charCapitalEnd - charCapitalStart) + (charLowerEnd - charLowerStart); // amount of the characters we want.
int firstGap = charCapitalStart - charNumEnd; // there are gaps of random characters between numbers and uppercase letters, so this allows us to skip those.
int secondGap = charLowerStart - charCapitalEnd; // similar to above, but between uppercase and lowercase letters.

// START generates a log to show us which characters we are considering for our UID.
NSMutableString *chars = [NSMutableString stringWithCapacity:amountOfChars];
for (int i = charNumStart; i <= charLowerEnd; i++) {
    if ((i >= charNumStart && i <= charNumEnd) || (i >= charCapitalStart && i <= charCapitalEnd) || (i >= charLowerStart && i <= charLowerEnd)) {
        [chars appendFormat:@"\n%c", (char) i];
    }
}
NSLog(@"chars: %@", chars);
// END log

// Generate a uid of 20 characters that chooses from our desired range.
int uidLength = 20;
NSMutableString *uid = [NSMutableString stringWithCapacity:uidLength];
for (int i = 0; i < uidLength; i++) {
    // Generate a random number within our character range.
    int randomNum = arc4random() % amountOfChars;
    // Add the lowest value number to line this up with a desirable character.
    randomNum += charNumStart;
    // if the number is in the letter range, skip over the characters between the numbers and letters.
    if (randomNum > charNumEnd) {
        randomNum += firstGap;
    }
    // if the number is in the lowercase letter range, skip over the characters between the uppercase and lowercase letters.
    if (randomNum > charCapitalEnd) {
        randomNum += secondGap;
    }
    // append the chosen character.
    [uid appendFormat:@"%c", (char) randomNum];
}
NSLog(@"uid: %@", uid);

// Generate a UID that selects any kind of character, including a lot of punctuation. It's a bit easier to do it this way.
int amountOfAnyCharacters = charLowerEnd - charNumStart; // A new range of characters.
NSMutableString *multiCharUid = [NSMutableString stringWithCapacity:uidLength];
for (int i = 0; i < uidLength; i++) {
    // Generate a random number within our new character range.
    int randomNum = arc4random() % amountOfAnyCharacters;
    // Add the lowest value number to line this up with our range of characters.
    randomNum += charNumStart;
    // append the chosen character.
    [multiCharUid appendFormat:@"%c", (char) randomNum];
}
NSLog(@"multiCharUid: %@", multiCharUid);

When I'm doing random character generation, I prefer to work directly with integers and cast them over, instead of writing out the list of chars that I want to draw from. Declaring the variables at the top makes it more system independent, but this code assumes that numbers will have a lower value than letters, and that uppercase letters will have a lower value than lowercase letters.

当我在做随机字符生成时,我喜欢直接使用整数并把它们转换成整数,而不是写出我想要从中提取的字符列表。在顶部声明变量使它更独立于系统,但这段代码假设数字的值将低于字母,大写字母的值将低于小写字母。

#9


4  

Swift

斯威夫特

func randomStringWithLength(length: Int) -> String {
    let alphabet = "-_1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
    let upperBound = UInt32(count(alphabet))
    return String((0..<length).map { _ -> Character in
        return alphabet[advance(alphabet.startIndex, Int(arc4random_uniform(upperBound)))]
    })
}

#10


3  

Alternative solution in Swift

在迅速替代解决方案

func generateString(len: Int) -> String {
    let letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
    let lettersLength = UInt32(countElements(letters))
    let result = (0..<len).map { _ -> String in
        let idx = Int(arc4random_uniform(lettersLength))
        return String(letters[advance(letters.startIndex, idx)])
    }
    return "".join(result)
}

#11


2  

Adding to good answer given by Melvin, here is a function I made (in SWIFT!) to get a random string:

梅尔文给出了一个很好的答案,下面是我做的一个函数(用SWIFT!)来获得一个随机字符串:

func randomStringOfLength(length:Int)->String{
    var wantedCharacters:NSString="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXZY0123456789"
    var s=NSMutableString(capacity: length)
    for (var i:Int = 0; i < length; i++) {
        let r:UInt32 = arc4random() % UInt32( wantedCharacters.length)
        let c:UniChar = wantedCharacters.characterAtIndex( Int(r) )
        s.appendFormat("%C", c)
    }
    return s
}

Here is a test result from calling randomStringOfLength(10): uXa0igA8wm

下面是调用randomStringOfLength(10)的测试结果:uXa0igA8wm

#12


2  

Generates lowercase alphanumeric random string with given length:

生成给定长度的小写字母数字随机字符串:

-(NSString*)randomStringWithLength:(NSUInteger)length
{
    NSMutableString* random = [NSMutableString stringWithCapacity:length];

    for (NSUInteger i=0; i<length; i++)
    {
        char c = '0' + (unichar)arc4random()%36;
        if(c > '9') c += ('a'-'9'-1);
        [random appendFormat:@"%c", c];
    }

    return random;
}

#13


1  

If you want a random unicode string, you can create random bytes and then use the valid ones.

如果您想要一个随机的unicode字符串,您可以创建随机字节,然后使用有效的字节。

    OSStatus sanityCheck = noErr;
    uint8_t * randomBytes = NULL;
    size_t length = 200; // can of course be variable

    randomBytes = malloc( length * sizeof(uint8_t) );
    memset((void *)randomBytes, 0x0, length);

    sanityCheck = SecRandomCopyBytes(kSecRandomDefault, length, randomBytes);

    if (sanityCheck != noErr) NSLog(@"Error generating random bytes, OSStatus == %ld.", sanityCheck);

    NSData* randomData = [[NSData alloc] initWithBytes:(const void *)randomBytes length: length];
    if (randomBytes) free(randomBytes);

    NSString* dataString = [[NSString alloc] initWithCharacters:[randomData bytes] length:[randomData length]];  // create an NSString from the random bytes
    NSData* tempData = [dataString dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];             // remove illegal characters from string
    NSString* randomString = [[NSString alloc] initWithData:tempData encoding:NSUTF8StringEncoding];

The conversion from NSString to NSData and back is necessary to get a valid UTF-8 string. Be aware that length will not necessarily be the length of the the NSString created in the end.

要获得有效的UTF-8字符串,必须从NSString转换到NSData并返回。请注意,长度不一定是最后创建的NSString的长度。

#14


1  

I did this using a simple char[] instead of an NSString * for the alphabet. I added this to a NSString category.

我使用了一个简单的char[]代替了字母表中的NSString *。我将它添加到NSString类别中。

static const char __alphabet[] =
    "0123456789"
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    "abcdefghijklmnopqrstuvwxyz";
+ (NSString *)randomString:(int)length
{
    NSMutableString *randomString = [NSMutableString stringWithCapacity:length];
    u_int32_t alphabetLength = (u_int32_t)strlen(__alphabet);
    for (int i = 0; i < length; i++) {
        [randomString appendFormat:@"%c", __alphabet[arc4random_uniform(alphabetLength)]];
    }
    return randomString;
}

#15


1  

static NSUInteger length = 32;
static NSString *letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
NSMutableString * randomString = [NSMutableString stringWithCapacity:length];
for (NSInteger i = 0; i < length; ++i) {
    [randomString appendFormat: @"%C", [letters characterAtIndex:(NSUInteger)arc4random_uniform((u_int32_t)[letters length])]];
}

#16


1  

Method to call:

方法调用:


NSString *string = [self stringWithRandomSuffixForFile:@"file.pdf" withLength:4]

Method:

方法:


- (NSString *)stringWithRandomSuffixForFile:(NSString *)file withLength:(int)length
{
    NSString *alphabet = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    NSString *fileExtension = [file pathExtension];
    NSString *fileName = [file stringByDeletingPathExtension];
    NSMutableString *randomString = [NSMutableString stringWithFormat:@"%@_", fileName];

    for (int x = 0; x < length; x++) {
        [randomString appendFormat:@"%C", [alphabet characterAtIndex: arc4random_uniform((int)[alphabet length]) % [alphabet length]]];
    }
    [randomString appendFormat:@".%@", fileExtension];

    NSLog(@"## randomString: %@ ##", randomString);
    return randomString;
}

Results:

结果:


## randomString: file_Msci.pdf ##
## randomString: file_xshG.pdf ##
## randomString: file_abAD.pdf ##
## randomString: file_HVwV.pdf ##

#17


1  

for Swift 3.0

斯威夫特3.0

func randomString(_ length: Int) -> String {

    let letters : NSString = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
    let len = UInt32(letters.length)

    var randomString = ""

    for _ in 0 ..< length {
        let rand = arc4random_uniform(len)
        var nextChar = letters.character(at: Int(rand))
        randomString += NSString(characters: &nextChar, length: 1) as String
    }

    return randomString
}

#18


1  

Modification of a few ideas here, and in done Swift 4.0

在这里修改一些想法,并在Swift 4.0中完成

extension String
{
    subscript (i: Int) -> Character
    {
        return self[index(startIndex, offsetBy:i)]
    }

    static func Random(length:Int=32, alphabet:String="ABCDEF0123456789") -> String
    {
        let upperBound = UInt32(alphabet.count)
        return String((0..<length).map { _ -> Character in
            return alphabet[Int(arc4random_uniform(upperBound))]
        })
    }
}

Usage:

用法:

let myHexString = String.Random()
let myLongHexString = String.Random(length:64)
let myLettersString = String.Random(length:32, alphabet:"ABCDEFGHIJKLMNOPQRSTUVWXYZ")

#19


0  

#define ASCII_START_NUMERS 0x30
#define ASCII_END_NUMERS 0x39
#define ASCII_START_LETTERS_A 0x41
#define ASCII_END_LETTERS_Z 0x5A
#define ASCII_START_LETTERS_a 0x61
#define ASCII_END_LETTERS_z 0x5A

-(NSString *)getRandomString:(int)length {
    NSMutableString *result = [[NSMutableString alloc]init];
    while (result.length != length) {
        NSMutableData* data = [NSMutableData dataWithLength:1];
        SecRandomCopyBytes(kSecRandomDefault, 1, [data mutableBytes]);
        Byte currentChar = 0;
        [data getBytes:&currentChar length:1];
        NSString *s = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        if (currentChar > ASCII_START_NUMERS && currentChar < ASCII_END_NUMERS) { // 0 to 0
            [result appendString:s];
            continue;
        }
        if (currentChar > ASCII_START_LETTERS_A && currentChar < ASCII_END_LETTERS_Z) { // 0 to 0
            [result appendString:s];
            continue;
        }
        if (currentChar > ASCII_START_LETTERS_a && currentChar < ASCII_END_LETTERS_z) { // 0 to 0
            [result appendString:s];
            continue;
        }
    }
    return result;
}

#20


0  

Modification for keithyip's answer:

修改keithyip的回答:

+ (NSString *)randomAlphanumericStringWithLength:(NSInteger)length
{
    static NSString * const letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        srand(time(NULL));
    });

    NSMutableString *randomString = [NSMutableString stringWithCapacity:length];

    for (int i = 0; i < length; i++) {
        [randomString appendFormat:@"%C", [letters characterAtIndex:arc4random() % [letters length]]];
    }

    return randomString;
}

#1


302  

Here's a quick and dirty implementation. Hasn't been tested.

这里有一个快速而肮脏的实现。还没有测试。

NSString *letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

-(NSString *) randomStringWithLength: (int) len {

    NSMutableString *randomString = [NSMutableString stringWithCapacity: len];

    for (int i=0; i<len; i++) {
         [randomString appendFormat: @"%C", [letters characterAtIndex: arc4random_uniform([letters length])]];
    }

    return randomString;
}

#2


92  

Not exactly what you ask, but still useful:

不完全是你问的,但仍然有用:

[[NSProcessInfo processInfo] globallyUniqueString]

Sample output:

样例输出:

450FEA63-2286-4B49-8ACC-9822C7D4356B-1376-00000239A4AC4FD5

#3


66  

NSString *alphabet  = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXZY0123456789";
NSMutableString *s = [NSMutableString stringWithCapacity:20];
for (NSUInteger i = 0U; i < 20; i++) {
    u_int32_t r = arc4random() % [alphabet length];
    unichar c = [alphabet characterAtIndex:r];
    [s appendFormat:@"%C", c];
}

#4


40  

Surely you can make this shorter:

当然你可以把它缩短:

+(NSString*)generateRandomString:(int)num {
    NSMutableString* string = [NSMutableString stringWithCapacity:num];
    for (int i = 0; i < num; i++) {
        [string appendFormat:@"%C", (unichar)('a' + arc4random_uniform(26))];
    }
    return string;
}

#5


23  

A category version of Jeff B's answer.

杰夫B答案的一个分类版本。

NSString+Random.h

NSString + Random.h

#import <Foundation/Foundation.h>

@interface NSString (Random)

+ (NSString *)randomAlphanumericStringWithLength:(NSInteger)length;

@end

NSString+Random.m

NSString + Random.m

#import "NSString+Random.h"

 @implementation NSString (Random)

+ (NSString *)randomAlphanumericStringWithLength:(NSInteger)length
{ 
    NSString *letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    NSMutableString *randomString = [NSMutableString stringWithCapacity:length];

    for (int i = 0; i < length; i++) {
        [randomString appendFormat:@"%C", [letters characterAtIndex:arc4random() % [letters length]]];
    }

    return randomString;
}

@end

#6


19  

If you're willing to limit yourself to hex characters only, then the simplest option is to generate a UUID:

如果您愿意只使用十六进制字符,那么最简单的选择就是生成UUID:

NSString *uuid = [NSUUID UUID].UUIDString;

Example output: 16E3DF0B-87B3-4162-A1A1-E03DB2F59654.

示例输出:16 e3df0b - 87 - b3 - 4162 - a1a1 e03db2f59654。

If you want a smaller random string then you can grab just the first 8 characters.

如果你想要一个更小的随机字符串,你可以只抓取前8个字符。

It's a version 4 UUID which means the first character in the 3rd and 4th group is not random (they will always be 4 and one of 8, 9, A or B).

它是一个版本4 UUID,意思是第三和第四组中的第一个字符不是随机的(它们总是4和8、9、a或B中的一个)。

Every other character in the string is fully random and you can generate millions of UUIDs every second for hundreds of years without much risk of the same UUID being generated twice.

字符串中的所有其他字符都是完全随机的,您可以在数百年的时间内每秒生成数百万个UUID,而不会产生两次相同的UUID。

#7


6  

You could also just generate a UUID. While not truly random, they are complex and unique which makes them appear random for most uses. Generate one as a string and then take a range of characters equal to the passed length.

还可以生成UUID。虽然不是真正的随机,但它们是复杂和独特的,这使它们在大多数情况下显得随机。生成一个字符串,然后取等于传递长度的字符范围。

#8


4  

Here's a different way to tackle it. Instead of using a prepared string of characters, you can cast between integers and characters, and generate a dynamic list of characters to select. It's pretty lean and fast, but has a bit more code.

这里有一种不同的解决方法。您可以在整数和字符之间强制转换,并生成要选择的动态字符列表,而不是使用准备好的字符字符串。它非常紧凑和快速,但是有更多的代码。

int charNumStart = (int) '0';
int charNumEnd = (int) '9';
int charCapitalStart = (int) 'A';
int charCapitalEnd = (int) 'Z';
int charLowerStart = (int) 'a';
int charLowerEnd = (int) 'z';

int amountOfChars = (charNumEnd - charNumStart) + (charCapitalEnd - charCapitalStart) + (charLowerEnd - charLowerStart); // amount of the characters we want.
int firstGap = charCapitalStart - charNumEnd; // there are gaps of random characters between numbers and uppercase letters, so this allows us to skip those.
int secondGap = charLowerStart - charCapitalEnd; // similar to above, but between uppercase and lowercase letters.

// START generates a log to show us which characters we are considering for our UID.
NSMutableString *chars = [NSMutableString stringWithCapacity:amountOfChars];
for (int i = charNumStart; i <= charLowerEnd; i++) {
    if ((i >= charNumStart && i <= charNumEnd) || (i >= charCapitalStart && i <= charCapitalEnd) || (i >= charLowerStart && i <= charLowerEnd)) {
        [chars appendFormat:@"\n%c", (char) i];
    }
}
NSLog(@"chars: %@", chars);
// END log

// Generate a uid of 20 characters that chooses from our desired range.
int uidLength = 20;
NSMutableString *uid = [NSMutableString stringWithCapacity:uidLength];
for (int i = 0; i < uidLength; i++) {
    // Generate a random number within our character range.
    int randomNum = arc4random() % amountOfChars;
    // Add the lowest value number to line this up with a desirable character.
    randomNum += charNumStart;
    // if the number is in the letter range, skip over the characters between the numbers and letters.
    if (randomNum > charNumEnd) {
        randomNum += firstGap;
    }
    // if the number is in the lowercase letter range, skip over the characters between the uppercase and lowercase letters.
    if (randomNum > charCapitalEnd) {
        randomNum += secondGap;
    }
    // append the chosen character.
    [uid appendFormat:@"%c", (char) randomNum];
}
NSLog(@"uid: %@", uid);

// Generate a UID that selects any kind of character, including a lot of punctuation. It's a bit easier to do it this way.
int amountOfAnyCharacters = charLowerEnd - charNumStart; // A new range of characters.
NSMutableString *multiCharUid = [NSMutableString stringWithCapacity:uidLength];
for (int i = 0; i < uidLength; i++) {
    // Generate a random number within our new character range.
    int randomNum = arc4random() % amountOfAnyCharacters;
    // Add the lowest value number to line this up with our range of characters.
    randomNum += charNumStart;
    // append the chosen character.
    [multiCharUid appendFormat:@"%c", (char) randomNum];
}
NSLog(@"multiCharUid: %@", multiCharUid);

When I'm doing random character generation, I prefer to work directly with integers and cast them over, instead of writing out the list of chars that I want to draw from. Declaring the variables at the top makes it more system independent, but this code assumes that numbers will have a lower value than letters, and that uppercase letters will have a lower value than lowercase letters.

当我在做随机字符生成时,我喜欢直接使用整数并把它们转换成整数,而不是写出我想要从中提取的字符列表。在顶部声明变量使它更独立于系统,但这段代码假设数字的值将低于字母,大写字母的值将低于小写字母。

#9


4  

Swift

斯威夫特

func randomStringWithLength(length: Int) -> String {
    let alphabet = "-_1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
    let upperBound = UInt32(count(alphabet))
    return String((0..<length).map { _ -> Character in
        return alphabet[advance(alphabet.startIndex, Int(arc4random_uniform(upperBound)))]
    })
}

#10


3  

Alternative solution in Swift

在迅速替代解决方案

func generateString(len: Int) -> String {
    let letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
    let lettersLength = UInt32(countElements(letters))
    let result = (0..<len).map { _ -> String in
        let idx = Int(arc4random_uniform(lettersLength))
        return String(letters[advance(letters.startIndex, idx)])
    }
    return "".join(result)
}

#11


2  

Adding to good answer given by Melvin, here is a function I made (in SWIFT!) to get a random string:

梅尔文给出了一个很好的答案,下面是我做的一个函数(用SWIFT!)来获得一个随机字符串:

func randomStringOfLength(length:Int)->String{
    var wantedCharacters:NSString="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXZY0123456789"
    var s=NSMutableString(capacity: length)
    for (var i:Int = 0; i < length; i++) {
        let r:UInt32 = arc4random() % UInt32( wantedCharacters.length)
        let c:UniChar = wantedCharacters.characterAtIndex( Int(r) )
        s.appendFormat("%C", c)
    }
    return s
}

Here is a test result from calling randomStringOfLength(10): uXa0igA8wm

下面是调用randomStringOfLength(10)的测试结果:uXa0igA8wm

#12


2  

Generates lowercase alphanumeric random string with given length:

生成给定长度的小写字母数字随机字符串:

-(NSString*)randomStringWithLength:(NSUInteger)length
{
    NSMutableString* random = [NSMutableString stringWithCapacity:length];

    for (NSUInteger i=0; i<length; i++)
    {
        char c = '0' + (unichar)arc4random()%36;
        if(c > '9') c += ('a'-'9'-1);
        [random appendFormat:@"%c", c];
    }

    return random;
}

#13


1  

If you want a random unicode string, you can create random bytes and then use the valid ones.

如果您想要一个随机的unicode字符串,您可以创建随机字节,然后使用有效的字节。

    OSStatus sanityCheck = noErr;
    uint8_t * randomBytes = NULL;
    size_t length = 200; // can of course be variable

    randomBytes = malloc( length * sizeof(uint8_t) );
    memset((void *)randomBytes, 0x0, length);

    sanityCheck = SecRandomCopyBytes(kSecRandomDefault, length, randomBytes);

    if (sanityCheck != noErr) NSLog(@"Error generating random bytes, OSStatus == %ld.", sanityCheck);

    NSData* randomData = [[NSData alloc] initWithBytes:(const void *)randomBytes length: length];
    if (randomBytes) free(randomBytes);

    NSString* dataString = [[NSString alloc] initWithCharacters:[randomData bytes] length:[randomData length]];  // create an NSString from the random bytes
    NSData* tempData = [dataString dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];             // remove illegal characters from string
    NSString* randomString = [[NSString alloc] initWithData:tempData encoding:NSUTF8StringEncoding];

The conversion from NSString to NSData and back is necessary to get a valid UTF-8 string. Be aware that length will not necessarily be the length of the the NSString created in the end.

要获得有效的UTF-8字符串,必须从NSString转换到NSData并返回。请注意,长度不一定是最后创建的NSString的长度。

#14


1  

I did this using a simple char[] instead of an NSString * for the alphabet. I added this to a NSString category.

我使用了一个简单的char[]代替了字母表中的NSString *。我将它添加到NSString类别中。

static const char __alphabet[] =
    "0123456789"
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    "abcdefghijklmnopqrstuvwxyz";
+ (NSString *)randomString:(int)length
{
    NSMutableString *randomString = [NSMutableString stringWithCapacity:length];
    u_int32_t alphabetLength = (u_int32_t)strlen(__alphabet);
    for (int i = 0; i < length; i++) {
        [randomString appendFormat:@"%c", __alphabet[arc4random_uniform(alphabetLength)]];
    }
    return randomString;
}

#15


1  

static NSUInteger length = 32;
static NSString *letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
NSMutableString * randomString = [NSMutableString stringWithCapacity:length];
for (NSInteger i = 0; i < length; ++i) {
    [randomString appendFormat: @"%C", [letters characterAtIndex:(NSUInteger)arc4random_uniform((u_int32_t)[letters length])]];
}

#16


1  

Method to call:

方法调用:


NSString *string = [self stringWithRandomSuffixForFile:@"file.pdf" withLength:4]

Method:

方法:


- (NSString *)stringWithRandomSuffixForFile:(NSString *)file withLength:(int)length
{
    NSString *alphabet = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    NSString *fileExtension = [file pathExtension];
    NSString *fileName = [file stringByDeletingPathExtension];
    NSMutableString *randomString = [NSMutableString stringWithFormat:@"%@_", fileName];

    for (int x = 0; x < length; x++) {
        [randomString appendFormat:@"%C", [alphabet characterAtIndex: arc4random_uniform((int)[alphabet length]) % [alphabet length]]];
    }
    [randomString appendFormat:@".%@", fileExtension];

    NSLog(@"## randomString: %@ ##", randomString);
    return randomString;
}

Results:

结果:


## randomString: file_Msci.pdf ##
## randomString: file_xshG.pdf ##
## randomString: file_abAD.pdf ##
## randomString: file_HVwV.pdf ##

#17


1  

for Swift 3.0

斯威夫特3.0

func randomString(_ length: Int) -> String {

    let letters : NSString = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
    let len = UInt32(letters.length)

    var randomString = ""

    for _ in 0 ..< length {
        let rand = arc4random_uniform(len)
        var nextChar = letters.character(at: Int(rand))
        randomString += NSString(characters: &nextChar, length: 1) as String
    }

    return randomString
}

#18


1  

Modification of a few ideas here, and in done Swift 4.0

在这里修改一些想法,并在Swift 4.0中完成

extension String
{
    subscript (i: Int) -> Character
    {
        return self[index(startIndex, offsetBy:i)]
    }

    static func Random(length:Int=32, alphabet:String="ABCDEF0123456789") -> String
    {
        let upperBound = UInt32(alphabet.count)
        return String((0..<length).map { _ -> Character in
            return alphabet[Int(arc4random_uniform(upperBound))]
        })
    }
}

Usage:

用法:

let myHexString = String.Random()
let myLongHexString = String.Random(length:64)
let myLettersString = String.Random(length:32, alphabet:"ABCDEFGHIJKLMNOPQRSTUVWXYZ")

#19


0  

#define ASCII_START_NUMERS 0x30
#define ASCII_END_NUMERS 0x39
#define ASCII_START_LETTERS_A 0x41
#define ASCII_END_LETTERS_Z 0x5A
#define ASCII_START_LETTERS_a 0x61
#define ASCII_END_LETTERS_z 0x5A

-(NSString *)getRandomString:(int)length {
    NSMutableString *result = [[NSMutableString alloc]init];
    while (result.length != length) {
        NSMutableData* data = [NSMutableData dataWithLength:1];
        SecRandomCopyBytes(kSecRandomDefault, 1, [data mutableBytes]);
        Byte currentChar = 0;
        [data getBytes:&currentChar length:1];
        NSString *s = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        if (currentChar > ASCII_START_NUMERS && currentChar < ASCII_END_NUMERS) { // 0 to 0
            [result appendString:s];
            continue;
        }
        if (currentChar > ASCII_START_LETTERS_A && currentChar < ASCII_END_LETTERS_Z) { // 0 to 0
            [result appendString:s];
            continue;
        }
        if (currentChar > ASCII_START_LETTERS_a && currentChar < ASCII_END_LETTERS_z) { // 0 to 0
            [result appendString:s];
            continue;
        }
    }
    return result;
}

#20


0  

Modification for keithyip's answer:

修改keithyip的回答:

+ (NSString *)randomAlphanumericStringWithLength:(NSInteger)length
{
    static NSString * const letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        srand(time(NULL));
    });

    NSMutableString *randomString = [NSMutableString stringWithCapacity:length];

    for (int i = 0; i < length; i++) {
        [randomString appendFormat:@"%C", [letters characterAtIndex:arc4random() % [letters length]]];
    }

    return randomString;
}