IOS开发基础知识--碎片45

1:iOS SEL的简单总结

SEL就是对方法的一种包装。包装的SEL类型数据它对应相应的方法地址，找到方法地址就可以调用方法

a.方法的存储位置

在内存中每个类的方法都存储在类对象中

每个方法都有一个与之对应的SEL类型的数据

根据一个SEL数据就可以找到对应的方法地址，进而调用方法

SEL类型的定义:  typedef struct objc_selector *SEL

b.SEL对象的创建

SEL s1 = @selector(test1); 　　// 将test1方法包装成SEL对象　

SEL s2 = NSSelectorFromString(@"test1"); 　　// 将一个字符串方法转换成为SEL对象

c.SEL对象的其他用法

// 将SEL对象转换为NSString对象　　

NSString *str = NSStringFromSelector(@selector(test));

实例：

Person *p = [Person new];

// 调用对象p的test方法

[p performSelector:@selector(test)];

[person performSelector:@selector(test2:) withObject:@"传入参数"];

Person类代码：

#import "Person.h"
@implementation Person
- (void)test
{
    NSLog(@"无参数的对象方法");
}
- (void)test2:(NSString *)str
{
    NSLog(@"带有参数的方法%@",str);
}
@end

d：在数组中的运用

// 对一个数组array的每个元素执行一次test方法

[array makeObjectsPerformSelector:@selector(test)];

[array makeObjectsPerformSelector:@selector(test)  withObject:@"aaa"];
//对一个数组array进行排序

[array sortedArrayUsingSelector:@selector(compare:)];

e:关于Sel传参运用(target - action设计模式)

在Button中我们经常用下面进行事件增加代码：

- (void)addTarget:(nullable id)target action:(SEL)action forControlEvents:(UIControlEvents)controlEvents;

实例：

#import <UIKit/UIKit.h>

@interface TapView : UIView
//目标
@property(weak,nonatomic)id target;
//行为
@property(assign,nonatomic)SEL action;

//自定义方法
-(void)addCustomtarget:(id)target andAction:(SEL)action;

@end

#import "TapView.h"

@implementation TapView

//自定义方法
-(void)addCustomtarget:(id)target andAction:(SEL)action{
    _action = action;
    _target = target;
}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    //当视图点击的时候,target去执行action的方法并把自己传过去.
    //首先代理不能是空,而且代理(代理是对象!)的类中有方法并且能传出过来.
    if (nil != _target && [[_target class] instancesRespondToSelector:_action]) {
        [_target performSelector:_action withObject:self];
    }
}

另一个实例：

#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#import "Debug.h" // not given; just an assert

@interface NSObject (Extras)

// Enforce the rule that the selector used must return void.
- (void) performVoidReturnSelector:(SEL)aSelector withObject:(id)object;
- (void) performVoidReturnSelector:(SEL)aSelector;

@end

@implementation NSObject (Extras)

// Apparently the reason the regular performSelect gives a compile time warning is that the system doesn't know the return type. I'm going to (a) make sure that the return type is void, and (b) disable this warning
// See http://*.com/questions/7017281/performselector-may-cause-a-leak-because-its-selector-is-unknown

- (void) checkSelector:(SEL)aSelector {
    // See http://*.com/questions/14602854/objective-c-is-there-a-way-to-check-a-selector-return-value
    Method m = class_getInstanceMethod([self class], aSelector);
    char type[];
    method_getReturnType(m, type, sizeof(type));

    NSString *message = [[NSString alloc] initWithFormat:@"NSObject+Extras.performVoidReturnSelector: %@.%@ selector (type: %s)", [self class], NSStringFromSelector(aSelector), type];
    NSLog(@"%@", message);

    if (type[] != 'v') {
        message = [[NSString alloc] initWithFormat:@"%@ was not void", message];
        [Debug assertTrue:FALSE withMessage:message];
    }
}

- (void) performVoidReturnSelector:(SEL)aSelector withObject:(id)object {
    [self checkSelector:aSelector];

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
    // Since the selector (aSelector) is returning void, it doesn't make sense to try to obtain the return result of performSelector. In fact, if we do, it crashes the app.
    [self performSelector: aSelector withObject: object];
#pragma clang diagnostic pop
}

- (void) performVoidReturnSelector:(SEL)aSelector {
    [self checkSelector:aSelector];

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
    [self performSelector: aSelector];
#pragma clang diagnostic pop
}

@end

2:代理模式实例

#import <UIKit/UIKit.h>

@protocol TouchViewDelegate <NSObject>
-(void)changeViewColor:(UIColor *)color;
@end

@interface TouchView : UIView
//声明一个代理,这个代理遵守TouchViewDelegate协议,
@property(nonatomic,assign)id<TouchViewDelegate> delegate;
@end

#import "TouchView.h"

@implementation TouchView

//我们还是用touchesBegandian
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{

    if (nil != self.delegate && [self.delegate respondsToSelector:@selector(changeViewColor:)]) {
        //我们传一个颜色到我们的ViewController去.
        [self.delegate changeViewColor:[UIColor brownColor]];
    }
}

@end

运用代码：

#import "ViewController.h"
#import "TouchView.h"

//在这里ViewController 要遵守协议....
@interface ViewController ()<TouchViewDelegate>

@property(nonatomic,strong)TouchView *touchView;

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    self.touchView = [[TouchView alloc]initWithFrame:CGRectMake(, , , )];

    self.touchView.backgroundColor = [UIColor redColor];
    //指定touchView的代理为ViewController.即为本身~
    self.touchView.delegate =self;

    [self.view addSubview: self.touchView];
}

-(void)changeViewColor:(UIColor *)color{
    //现在参数color是有值的,这是因为在TouchView那个页面传过来的.
    self.touchView.backgroundColor = color;
}
@end

3:关于Bolck运用

#import <UIKit/UIKit.h>

//给block改名成MyBlock
typedef void(^MyBlock)(NSString *);

@interface OtherViewController : UIViewController

//ARC:语义设置使用strong即可
@property(nonatomic,strong)MyBlock block;

@end

#import "OtherViewController.h"

@interface OtherViewController ()
@property(nonatomic,strong)UITextField *textField;
@end

@implementation OtherViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.textField = [[UITextField alloc]initWithFrame:CGRectMake(, , , )];
    self.textField.backgroundColor = [UIColor lightGrayColor];
    self.view.backgroundColor = [UIColor whiteColor];
    [self.view addSubview: self.textField];
}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    self.block(_textField.text);
    [self.navigationController popViewControllerAnimated:YES];
}
@end

运用代码：

    OtherViewController *otherVC = [[OtherViewController alloc]init];
    __weak typeof(self)weak = self;
    //给block赋值~
    otherVC.block = ^(NSString *string){
        weak.label.text = string;
    };

    [self.navigationController pushViewController:otherVC animated:YES];

4:UIButton的几种触发方式

a、UIControlEventTouchDown

　　指鼠标左键按下（注：只是“按下”）的动作

b、UIControlEventTouchDownRepeat

　　指鼠标左键连续多次重复按下（注：只是“按下”）的动作，比如，鼠标连续双击、三击、……、多次连击。

　　说明：多次重复按下时，事件序列是这样的：

　　UIControlEventTouchDown ->

　　(UIControlEventTouchUpInside) ->

　　UIControlEventTouchDown -> 

　　UIControlEventTouchDownRepeat -> 

　　(UIControlEventTouchUpInside) -> 

　　UIControlEventTouchDown -> 

　　UIControlEventTouchDownRepeat -> 

　　(UIControlEventTouchUpInside) ->

　　......

　　除了第一次按下外，后面每次摁下都是一个UIControlEventTouchDown事件，然后紧跟一个UIControlEventTouchDownRepeat事件。

c、UIControlEventTouchDragInside

　　指按下鼠标，然后在控件边界范围内拖动。

d、UIControlEventTouchDragOutside

　　与UIControlEventTouchDragInside不同的是，拖动时，鼠标位于控件边界范围之外。

　　但首先得有个UIControlEventTouchDown事件，然后接一个UIControlEventTouchDragInside事件，再接一个UIControlEventTouchDragExit事件，这时，鼠标已经位于控件外了，继续拖动就是UIControlEventTouchDragOutside事件了。

　　具体操作是：在控件里面按下鼠标，然后拖动到控件之外。

e、UIControlEventTouchDragEnter

　　指拖动动作中，从控件边界外到内时产生的事件。

f、UIControlEventTouchDragExit

　　指拖动动作中，从控件边界内到外时产生的事件。

g、UIControlEventTouchUpInside

　　指鼠标在控件范围内抬起，前提先得按下，即UIControlEventTouchDown或UIControlEventTouchDownRepeat事件。

h、UIControlEventTouchUpOutside

　　指鼠标在控件边界范围外抬起，前提先得按下，然后拖动到控件外，即 

　　UIControlEventTouchDown -> 

　　UIControlEventTouchDragInside(n 个) -> 

　　UIControlEventTouchDragExit -> 

　　UIControlEventTouchDragOutside(n 个) 

　　时间序列，再然后就是抬起鼠标，产生UIControlEventTouchUpOutside事件。

5:让编译器对一些警告闭嘴

a:方法弃用告警

#pragma clang diagnostic push  

#pragma clang diagnostic ignored "-Wdeprecated-declarations"
//会报警告的方法，比如SEL
[TestFlight setDeviceIdentifier:[[UIDevice currentDevice] uniqueIdentifier]];  

#pragma clang diagnostic pop  

b:未使用变量

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-variable"   

int a;   

#pragma clang diagnostic pop 

6:一个六边形，并只在六边形里面有点击效果

#import <UIKit/UIKit.h>
//六边形Button
@interface HexagonButton : UIView
NS_ASSUME_NONNULL_BEGIN

typedef void (^HexagonButtonBlock)();

@property (nonatomic, strong) UIBezierPath *path;
@property (nonatomic, strong) CAShapeLayer *maskLayer;
@property (nonatomic, strong) HexagonButtonBlock block; //点击事件

//添加点击事件

NS_ASSUME_NONNULL_END
@end

#import "HexagonButton.h"

@implementation HexagonButton
- (instancetype) initWithFrame:(CGRect)frame
{
    if ([super initWithFrame:frame]) {

        self.backgroundColor = [UIColor brownColor];
        self.userInteractionEnabled = YES;

        //添加单击手势
        UITapGestureRecognizer * tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(click:)];
        [self addGestureRecognizer:tap];
    }
    return self;
}
- (void) layoutSubviews
{
    [super layoutSubviews];
    CGFloat SIZE = self.frame.size.width;
    // step 1: 生成六边形路径
    CGFloat longSide = SIZE * 0.5 * cosf(M_PI *  / );
    CGFloat shortSide = SIZE * 0.5 * sin(M_PI *  / );
    CGFloat k = SIZE * 0.5 - longSide;  //路径整体下移，保证六边形路径位于图形中间

    _path = [UIBezierPath bezierPath];
    [_path moveToPoint:CGPointMake(, longSide  + k)];
    [_path addLineToPoint:CGPointMake(shortSide, + k)];
    [_path addLineToPoint:CGPointMake(shortSide + shortSide + shortSide,  k)];
    [_path addLineToPoint:CGPointMake(SIZE, longSide + k)];
    [_path addLineToPoint:CGPointMake(shortSide * , longSide *  + k)];
    [_path addLineToPoint:CGPointMake(shortSide, longSide *  + k)];
    [_path closePath];

    // step 2: 根据路径生成蒙板
    _maskLayer = [CAShapeLayer layer];
    //    _maskLayer.position = self.center;
    _maskLayer.path = [_path CGPath];

    // step 3: 添加蒙版
    self.layer.mask = _maskLayer;

    self.backgroundColor = [UIColor orangeColor];
}

//点击事件
- (void) click:(UITapGestureRecognizer *) tap
{
    if (_block) {
        _block();
    }
}
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event {
    //如果点击的区域在所创建的路径范围内
    if (CGPathContainsPoint(_path.CGPath, NULL, point, NO)) {
        return [super hitTest:point withEvent:event];
    }
    return nil;
}

@end

    //创建六变形按钮
    HexagonButton * hexagonButton = [[HexagonButton alloc] initWithFrame:CGRectMake(, , , )];
    hexagonButton.center = self.view.center;
    hexagonButton.block = ^(){
        NSLog(@"六边形区域被点击");
    };
    [self.view addSubview:hexagonButton];

7:self.navigationController.viewControllers修改

var controllerArr = self.navigationController?.viewControllers//获取Controller数组
controllerArr?.removeAll()//移除controllerArr中保存的历史路径
    //重新添加新的路径
controllerArr?.append(self.navigationController?.viewControllers[])
controllerArr?.append(C)
controllerArr?.append(B)
    //这时历史路径为（root -> c -> b）
    //将组建好的新的跳转路径 set进self.navigationController里
self.navigationController?.setViewControllers(controllerArr!, animated: true)//直接写入，完成跳转B页面的同时修改了之前的跳转路径

主要解决那些乱七八糟的转转，不按顺序来的问题；