是否可以在 NSMutableArray 中混合 addObject:? [英] is it possible to swizzle addObject: in NSMutableArray?

问题描述

NSMutableArray 的 addObject: 方法是否可以混合使用?

Is it possible to swizzle the addObject: method of NSMutableArray?

这就是我正在尝试的.

#import <Foundation/Foundation.h>
#import <objc/runtime.h>

@implementation NSMutableArray (LoggingAddObject)


+ (void)load {
Method addObject = class_getInstanceMethod(self, @selector(addObject:));
Method logAddObject = class_getInstanceMethod(self, @selector(logAddObject:));
method_exchangeImplementations(addObject, logAddObject);

Method original = class_getInstanceMethod(self, @selector(setObject:atIndexedSubscript:));
Method swizzled = class_getInstanceMethod(self, @selector(swizzled_setObject:atIndexedSubscript:));
method_exchangeImplementations(original, swizzled);
}


- (void)logAddObject:(id)anObject {
[self logAddObject:anObject];
NSLog(@"Added object %@ to array %@", anObject, self);
}

-(void)swizzled_setObject:(id)obj atIndexedSubscript:(NSUInteger)idx
{
NSLog(@"This gets called as expected!!-----");
[self swizzled_setObject:obj atIndexedSubscript:idx];  
}

我可以调配一些方法，例如 setObject:atIndexedSubscript: 但我担心我无法做到 addObject: 和其他方法.我认为下面不能调配?有人可以解释为什么吗?我做错了什么或解决这个问题的方法?

I am able to swizzle some of the methods like setObject:atIndexedSubscript: but I am worried that I cant do it do the addObject: and others. I think the below can not be swizzled? Can someone explain why ? what I am doing wrong and or a way around this?

/****************   Mutable Array       ****************/

@interface NSMutableArray : NSArray

- (void)addObject:(id)anObject;
- (void)insertObject:(id)anObject atIndex:(NSUInteger)index;
- (void)removeLastObject;
- (void)removeObjectAtIndex:(NSUInteger)index;
- (void)replaceObjectAtIndex:(NSUInteger)index withObject:(id)anObject;

@end

推荐答案

你可以用 NSProxy 试试这个，但我不建议你在生产代码中使用它，因为:

You can try this with NSProxy, but I don't suggest you to use it on production code because:

• 它会破坏某些东西(某些框架可能需要NSMutableArray在添加nil时抛出异常以防止以后出现更严重的错误.即快速失败)
• 很慢

• it will break something (some framework may require NSMutableArray to throw exception when add nil into it to prevent more serious error later. i.e. Fail fast)
• it is slow

如果你真的想避免 nil 检查，我建议你创建一个 NSMutableArray 的子类并在你的代码中到处使用它.但真的吗?使用NSMutableArray的ObjC代码太多了，大部分都不需要这个功能.那你为什么这么特别?

If you really want to avoid nil checking, I suggest you to make a subclass of NSMutableArray and use it everywhere in your code. But really? There are so many ObjC code using NSMutableArray, most of them doesn't need this feature. So why you are so special?

#import <objc/runtime.h>

@interface XLCProxy : NSProxy

+ (id)proxyWithObject:(id)obj;

@end

@implementation XLCProxy
{
    id _obj;
}

+ (void)load
{
    Method method = class_getClassMethod([NSMutableArray class], @selector(allocWithZone:));
    IMP originalImp = method_getImplementation(method);

    IMP imp = imp_implementationWithBlock(^id(id me, NSZone * zone) {
        id obj = ((id (*)(id,SEL,NSZone *))originalImp)(me, @selector(allocWithZone:), zone);
        return [XLCProxy proxyWithObject:obj];
    });

    method_setImplementation(method, imp);
}

+ (id)proxyWithObject:(id)obj
{
    XLCProxy *proxy = [self alloc];
    proxy->_obj = obj;
    return proxy;
}

- (void)forwardInvocation:(NSInvocation *)invocation
{
    [invocation setTarget:_obj];
    [invocation invoke];
    const char *selname = sel_getName([invocation selector]);
    if ([@(selname) hasPrefix:@"init"] && [[invocation methodSignature] methodReturnType][0] == '@') {
        const void * ret;
        [invocation getReturnValue:&ret];
        ret = CFBridgingRetain([XLCProxy proxyWithObject:CFBridgingRelease(ret)]);
        [invocation setReturnValue:&ret];
    }
}

-(NSMethodSignature *)methodSignatureForSelector:(SEL)sel
{
    return [_obj methodSignatureForSelector:sel];
}

- (Class)class
{
    return [_obj class];
}

- (void)addObject:(id)obj
{
    [_obj addObject:obj ?: [NSNull null]];
}

- (BOOL)isEqual:(id)object
{
    return [_obj isEqual:object];
}

- (NSUInteger)hash {
    return [_obj hash];
}

// you can add more methods to "override" methods in `NSMutableArray` 

@end

<小时>

@interface NSMutableArrayTests : XCTestCase

@end

@implementation NSMutableArrayTests

- (void)testExample
{
    NSMutableArray *array = [NSMutableArray array];
    [array addObject:nil];
    [array addObject:@1];
    [array addObject:nil];
    XCTAssertEqualObjects(array, (@[[NSNull null], @1, [NSNull null]]));
}

@end

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