关于实现多参数的performSel方法 , 以下是我的实现代码，由于这个方法的设定，必须返回一个对象，所以我对数值类型做了判断与类型的转换，(如果需要其他的类型，可以自己去添加)
/**
* @brief 根据方法名 参数 调用方法
* @param selector 方法名
* @param objects 参数数组
* @return 被调用的方法的返回值和参数都不支持结构体和block，仅仅支持基本数值类型和对象
*/
- (id)pa_performSelector:(SEL)selector withObjects:(NSArray *)objects
{
// 方法签名(方法的描述)
NSMethodSignature *signature = [[self class] instanceMethodSignatureForSelector:selector];
if (signature == nil) {
//可以抛出异常也可以不操作。
}
// NSInvocation : 利用一个NSInvocation对象包装一次方法调用（方法调用者、方法名、方法参数、方法返回值）
NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
invocation.target = self;
invocation.selector = selector;
//获取返回类型
const char *returnType = [signature methodReturnType];
// 判断返回值类型 根据类型转化数据类型
NSString *returnTypeString = [NSString stringWithUTF8String:returnType];
// 设置参数
NSInteger paramsCount = signature.numberOfArguments - 2; // 除self、_cmd以外的参数个数
paramsCount = MIN(paramsCount, objects.count);
for (int i = 0; i < paramsCount; i++) {
// 取出参数对象
id obj = objects[i];
// 判断需要设置的参数是否是NSNull, 如果是就设置为nil
if ([obj isKindOfClass:[NSNull class]]) {
obj = nil;
}
// 获取参数类型
const char *argumentType = [signature getArgumentTypeAtIndex:i + 2];
// 判断参数类型 根据类型转化数据类型
NSString *argumentTypeString = [NSString stringWithUTF8String:argumentType];
if ([argumentTypeString isEqualToString:@"@"]) { // id
[invocation setArgument:&obj atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"B"]) { // bool
bool objVaule = [obj boolValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"f"]) { // float
float objVaule = [obj floatValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"d"]) { // double
double objVaule = [obj doubleValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"c"]) { // char
char objVaule = [obj charValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"i"]) { // int
int objVaule = [obj intValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"I"]) { // unsigned int
unsigned int objVaule = [obj unsignedIntValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"S"]) { // unsigned short
unsigned short objVaule = [obj unsignedShortValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"L"]) { // unsigned long
unsigned long objVaule = [obj unsignedLongValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"s"]) { // shrot
short objVaule = [obj shortValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"l"]) { // long
long objVaule = [obj longValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"q"]) { // long long
long long objVaule = [obj longLongValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"C"]) { // unsigned char
unsigned char objVaule = [obj unsignedCharValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"Q"]) { // unsigned long long
unsigned long long objVaule = [obj unsignedLongLongValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"{CGRect={CGPoint=dd}{CGSize=dd}}"]) { // CGRect
CGRect objVaule = [obj CGRectValue];
[invocation setArgument:&objVaule atIndex:i + 2];
} else if ([argumentTypeString isEqualToString:@"{UIEdgeInsets=dddd}"]) { // UIEdgeInsets
UIEdgeInsets objVaule = [obj UIEdgeInsetsValue];
[invocation setArgument:&objVaule atIndex:i + 2];
}
}
// 调用方法
[invocation invoke];
id result ;
//获取返回值
if ([returnTypeString isEqualToString:@"@"]) { // id
void * returnValue;if (signature.methodReturnLength){[invocation getReturnValue:&returnValue];result= (__bridge id)returnValue; returnValue = nil;}else{result= nil;}
} else if ([returnTypeString isEqualToString:@"B"]) { // bool
bool returnValue;if (signature.methodReturnLength){[invocation getReturnValue:&returnValue]; result= [NSNumber numberWithBool:returnValue];}else{result= nil;}
} else if ([returnTypeString isEqualToString:@"f"]) { // float
float returnValue;if (signature.methodReturnLength){ [invocation getReturnValue:&returnValue]; result= [NSNumber numberWithFloat:returnValue];}else{result= nil;}
} else if ([returnTypeString isEqualToString:@"d"]) { // double
double returnValue;if (signature.methodReturnLength){[invocation getReturnValue:&returnValue]; result= [NSNumber numberWithDouble:returnValue];}else{result= nil;}
} else if ([returnTypeString isEqualToString:@"c"]) { // char
char returnValue;if (signature.methodReturnLength){ [invocation getReturnValue:&returnValue]; result= [NSNumber numberWithChar:returnValue];}else{result= nil;}
} else if ([returnTypeString isEqualToString:@"i"]) { // int
int returnValue; if (signature.methodReturnLength){[invocation getReturnValue:&returnValue]; result= [NSNumber numberWithInt:returnValue];}else{result= nil;}
} else if ([returnTypeString isEqualToString:@"I"]) { // unsigned int
unsigned int returnValue;if (signature.methodReturnLength){[invocation getReturnValue:&returnValue]; result= [NSNumber numberWithUnsignedInteger:returnValue];}else{result= nil;}
} else if ([returnTypeString isEqualToString:@"S"]) { // unsigned short
unsigned short returnValue;if (signature.methodReturnLength){[invocation getReturnValue:&returnValue]; result= [NSNumber numberWithUnsignedShort:returnValue];}else{result= nil;}
} else if ([returnTypeString isEqualToString:@"L"]) { // unsigned long
unsigned long returnValue;if (signature.methodReturnLength){[invocation getReturnValue:&returnValue]; result= [NSNumber numberWithUnsignedLong:returnValue];}else{result= nil;}
} else if ([returnTypeString isEqualToString:@"s"]) { // shrot
short returnValue;if (signature.methodReturnLength){[invocation getReturnValue:&returnValue]; result= [NSNumber numberWithShort:returnValue];}else{result= nil;}
} else if ([returnTypeString isEqualToString:@"l"]) { // long
long returnValue;if (signature.methodReturnLength){[invocation getReturnValue:&returnValue]; result= [NSNumber numberWithLong:returnValue];}else{result= nil;}
} else if ([returnTypeString isEqualToString:@"q"]) { // long long
long long returnValue;if (signature.methodReturnLength){[invocation getReturnValue:&returnValue]; result= [NSNumber numberWithLongLong:returnValue];}else{result= nil;}
} else if ([returnTypeString isEqualToString:@"C"]) { // unsigned char
unsigned char returnValue;if (signature.methodReturnLength){[invocation getReturnValue:&returnValue]; result= [NSNumber numberWithUnsignedChar:returnValue];}else{result= nil;}
} else if ([returnTypeString isEqualToString:@"Q"]) { // unsigned long long
unsigned long long returnValue;if (signature.methodReturnLength){[invocation getReturnValue:&returnValue]; result= [NSNumber numberWithUnsignedLongLong:returnValue];}else{result= nil;}
}else if([returnTypeString isEqualToString:@"v"]){
result= nil;
}else{
PA_THROW_EXCEPTION(@"不能识别的返回类型");
result= nil;
}
signature = nil;
invocation = nil;
return result;
// else if ([returnTypeString isEqualToString:@"{CGRect={CGPoint=dd}{CGSize=dd}}"]) { // CGRect
// CGRect returnValue;[invocation getReturnValue:&returnValue]; return [NSValue valueWithCGRect:returnValue];
// } else if ([returnTypeString isEqualToString:@"{UIEdgeInsets=dddd}"]) { // UIEdgeInsets
// UIEdgeInsets returnValue;[invocation getReturnValue:&returnValue]; return [NSValue valueWithUIEdgeInsets:returnValue];
// }
// @"{CGPoint=dd}" @"{CGSize=dd}" @"{UIOffset=dd}"
}
关于其他的实现方法发生崩溃的情况的详解
crash情况
刚开始实现这个方法的时候我也遇到过这种问题，其实这个问题其实是NSInvocation在获取返回值后crash问题
NSMethodSignature *signature = [[self class] instanceMethodSignatureForSelector:selector]
NSInvocation *invocation = [NSInvocation invocationWithMethodSignature: signature];
invocation.target = self;
invocation.selector = selector;
NSArray *resultSet;
[invocation invoke];
[invocation getReturnValue:&resultSet];
return resultSet;
在当我们执行getReturnValue的方法时，获取的返回值是一个对象的时候，app很快就会crash，注意，是很快，不是马上，所以程序crash后xcode也不会跳到这个位置来。因此，就会让人抓破脑袋去一句句代码注释调试。
当我把方法的返回值设置成
@"123"
常量形式的字符串的时候，程序是可以正常运行的，但是当我把返回值设置成
[@"123" stringByAppendingString:@"123"]
程序又会crash
解决问题
我找到了一段解析
在设置Enable Zombies后发现，是由于系统多次释放NSArray * resultSet造成的非法内存访问。
原因是在arc模式下，getReturnValue：仅仅是从invocation的返回值拷贝到指定的内存地址，如果返回值是一个NSObject对象的话，是没有处理起内存管理的。而我们在定义resultSet时使用的是__strong类型的指针对象，arc就会假设该内存块已被retain（实际没有），当resultSet出了定义域释放时，导致该crash。假如在定义之前有赋值的话，还会造成内存泄露的问题。
我试验了一下，发现真的如此，
其实这种情况下有两种解决方案
使用一个unretain的对象来获取返回值，或者 用void *指针来保存返回值，然后用__bridge来转化为OC对象。
id __unsafe_unretained returnValue;
[invocation getReturnValue:& returnValue];
id result = returnValue;
或者
// id
void * returnValue;
[invocation getReturnValue:&returnValue];
result= (__bridge id)returnValue;
思考
那么，为什么@"123"没事，而[@"123" stringByAppendingString:@"123"]会有事呢？
答案如下：
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