Question

我试图调动NSMutableDictionary。我在这做错了什么？我试图覆盖setObject：forKey：for NSMutableDictionary。

#import "NSMutableDictionary+NilHandled.h"
#import <objc/runtime.h>


@implementation NSMutableDictionary (NilHandled)

+ (void)load{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Class class = [self class];

        SEL originalSelector = @selector(setObject:forKey:);
        SEL swizzledSelector = @selector(swizzledSetObject:forKey:);

        Method originalMethod = class_getInstanceMethod(class, originalSelector);
        Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);

        class_replaceMethod(class, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));

        BOOL didAddMethod = class_addMethod(class,originalSelector,method_getImplementation(swizzledMethod),method_getTypeEncoding(swizzledMethod));
        if (didAddMethod) {
            class_replaceMethod(class,swizzledSelector,method_getImplementation(originalMethod),method_getTypeEncoding(originalMethod));
        } else {
            method_exchangeImplementations(originalMethod, swizzledMethod);
        }
    });
}

- (void) swizzledSetObject:(id)anObject forKey:(id<NSCopying>)aKey
{
    [self swizzledSetObject:anObject?anObject:@"Nil" forKey:aKey];
}

@end

Answer 1

NSMutableDictionary是class cluster。它是许多实现实际工作的Apple私有具体子类的抽象基类。作为子类，它们会覆盖-setObject:forKey:。 NSMutableDictionary本身没有真正实现该方法，也没有尝试调用它。因此，没有任何东西可以替代您的替代实施。

Answer 2

在被告知为什么它不起作用之后：只需向NSMutableDictionary添加一个新方法，如 - （void）setObject：（id）object orNullForKey：（NSString *）key。

可能更有用的是一种方法，如果它是零，则不会尝试添加或删除对象。这样，objectForKey将返回nil，与您传入的相同。

Answer 3

更改代码：

Class class = [self class];

收件人：

Class class = NSClassFromString(@"__NSDictionaryM");

为我工作，您可以尝试！

这是我的完整代码：

@implementation NSMutableDictionary (Category)

+ (void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
    [super load];
	Class class = NSClassFromString(@"__NSDictionaryM");
	SEL originalSelector = @selector(setObject:forKey:);
	SEL swizzledSelector = @selector(fu_setObject:forKey:);

    Method originalMethod = class_getInstanceMethod(class,originalSelector);
	Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
	BOOL didAddMethod =
		class_addMethod(class,
			originalSelector,
			method_getImplementation(swizzledMethod),
			method_getTypeEncoding(swizzledMethod));

	if (didAddMethod) {
		class_replaceMethod(class,
			swizzledSelector,
			method_getImplementation(originalMethod),
			method_getTypeEncoding(originalMethod));
	} else {
		method_exchangeImplementations(originalMethod, swizzledMethod);
	}
    });
}

-(void)fu_setObject:(id)anObject forKey:(id<NSCopying>)aKey{
   [self fu_setObject:anObject forKey:aKey];
   
}
@end

不会调用NSMutableDictionary的Swizzled方法

3 个答案: