处理unrecognized selector异常原因
假如封装一个方法，在其他模块调用该方法时，传入参数不匹配则crash。比如下面的方法：本应该传入的参数类型为NSMutableArray，如果传入的参数类型是NSArray，导致抛出 unrecognized selector异常
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- (void)doSomethingWithArray:(NSMutableArray *)arr{
[arr addObject:@"123"];
}
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当然，通过 参数类型判断 也可以避免问题的发生：
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- (void)doSomethingWithArray:(NSMutableArray *)arr{
if ([arr isKindOfClass:[NSMutableArray class]]) {
[arr addObject:@"123"];
}else{
CrashOnSimulator(@"⚠️参数类型不对哦⚠️");
}
}
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crash提醒：
但是，有点地方可能忘记类型判断了怎么办，有全局拦截unrecognized selector 异常的方案吗？
分析 如何全局拦截unrecognized selector 异常
oc的消息发送机制咱们都熟悉了，通过superclass指针逐级向上查找该消息所对应的方法实现，如果遇到找不的方法，还有三次补救机制。我们可以通过上面三种方法中的一种，就可以避免unrecognized selector sent to instance
第一种方法：重写 NSObject 的forwardingTargetForSelector:
⚠️filter unrecoginze seletor of intance only
思路
- 创建一个接收未知消息的类，暂且称之为
Protector - 创建一个
NSObject的分类，在分类中重写forwardingTargetForSelector: ，在这个方法中截获未实现的方法，转发给Protector。并为Protector动态的添加未实现的方法，最后返回Protector的实例对象。 - 在分类中新增一个安全的方法实现，来作为
Protector接收到的未知消息的实现
代码
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#import "NSObject+Protector.h"
#import <objc/runtime.h>
@implementation NSObject (Protector)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wobjc-protocol-method-implementation"
- (id)forwardingTargetForSelector:(SEL)aSelector{
if ([self isCurrentClassInWhiteList]) {
[[self class] warningDeveloper:aSelector];
Class protectorCls = NSClassFromString(@"ProtectorClassName");
if (!protectorCls){
protectorCls = objc_allocateClassPair([NSObject class], "ProtectorClassName", 0);
objc_registerClassPair(protectorCls);
}
if (![self isExistSelector:aSelector inClass:protectorCls]){
class_addMethod(protectorCls, aSelector, [self safeImplementation:aSelector],[NSStringFromSelector(aSelector) UTF8String]);
}
Class Protector = [protectorCls class];
id instance = [[Protector alloc] init];
return instance;
} else {
return nil;
}
}
#pragma clang diagnostic pop
- (BOOL)isCurrentClassInWhiteList{
NSArray *classNameArray = @[@"NSNull",@"NSString",@"NSArray",@"NSDictionary",@"NSURL"];
for (NSString *className in classNameArray) {
if ([self isKindOfClass:NSClassFromString(className)]) {
return YES;
}
}
return NO;
}
- (BOOL)isExistSelector: (SEL)aSelector inClass:(Class)currentClass{
BOOL isExist = NO;
unsigned int methodCount = 0;
Method *methods = class_copyMethodList(currentClass, &methodCount);
for (int i = 0; i < methodCount; i++){
Method temp = methods[i];
SEL sel = method_getName(temp);
NSString *methodName = NSStringFromSelector(sel);
if ([methodName isEqualToString: NSStringFromSelector(aSelector)]){
isExist = YES;
break;
}
}
return isExist;
}
- (IMP)safeImplementation:(SEL)aSelector{
IMP imp = imp_implementationWithBlock(^(){
NSLog(@"PROTECTOR: %@ Done", NSStringFromSelector(aSelector));
});
return imp;
}
+ (void)warningDeveloper:(SEL)aSelector{
#if DEBUG
NSString *selectorStr = NSStringFromSelector(aSelector);
NSLog(@"PROTECTOR: -[%@ %@]", [self class], selectorStr);
NSLog(@"PROTECTOR: unrecognized selector \"%@\" sent to instance: %p", selectorStr, self);
NSLog(@"PROTECTOR: call stack: %@", [NSThread callStackSymbols]);
// @throw @"方法找不到";
#endif
}
@end
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