是否可以在NSMutableArray中调配addObject:？

Question

是否可以调用NSMutableArray的addObject:方法？

这是我正在尝试的.

#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];  
}

我能够调整一些像setObject:atIndexedSubscript这样的方法:但我担心我不能这样做addObject:和其他人.我觉得下面不能调整？有人可以解释原因吗？我做错了什么或者解决这个问题？

/****************   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

Answer 1

您可以尝试使用NSProxy,但我不建议您在生产代码上使用它,因为:

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

如果你真的想避免nil检查,我建议你创建一个子类,NSMutableArray并在代码中的任何地方使用它.但真的吗？使用了很多ObjC代码NSMutableArray,其中大多数都不需要这个功能.那么为什么你如此特别？

#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

@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