防止unrecognized selector sent to instance錯誤

1 - 我們在開發過程中經常會遇到 unrecognized selector sent to instance 錯誤

2 - 程式碼示例：呼叫 Person中不存在的方法，程式不會 crash

// - Person.h

#import <Foundation/Foundation.h>
@interface Person : NSObject

-(void)run;

@end

// -Person.m

#import "Person.h"
@implementation Person

-(void
 
)run{
    
    NSLog(@"Person run.......");
}

// 方法簽名
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector{
    
    if ([self respondsToSelector:aSelector]) {
        return [super methodSignatureForSelector:aSelector];
    }
    
    // 返回找不到的方法
    return [NSMethodSignature signatureWithObjCTypes:"
 
v@:"];
}

// 找不到的方法都回來到這裡
- (void)forwardInvocation:(NSInvocation *)anInvocation{

    NSLog(@"找不到 %@方法",NSStringFromSelector(anInvocation.selector));
}
@end

// - main.m

#import <Foundation/Foundation.h>
#import "Person.h"
int main(int argc, const char * argv[]) {
    
    Person *p1 = [Person new
 
];
    // Person中只有 run方法
    [p1 run];
    
    // 呼叫不存在的方法
    [p1 makeTest];
    [p1 goTest];
    
    return 0;
    
}

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