相关疑难解决方法(0)

我可以使用类类别来覆盖已使用类别实现的方法吗？像这样:

1)原始方法

-(BOOL) method {
  return true;
}

2)覆盖方法

-(BOOL) method {
  NSLog(@"error?"); 
  return true; 
}

这会起作用,还是非法的？

我使用以下代码为UINavigationBar创建了一个类别:

// UINavigationBar+MyNavigationBar.m
@interface UINavigationBar (MyNavigationBar)

@end

@implementation UINavigationBar (MyNavigationBar)

- (void)drawRect:(CGRect)rect
{
    UIImage *img = [UIImage imageNamed: @"header.png"];
    [img drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
}

@end

我没有在任何地方#import,在我的整个项目的任何代码中,但是,此类别仍在运行并插入标题图形.这怎么可能？

我注意到UIImageView上的AFNetworking和SDWebImage类别具有相同的方法名称.

AFNetworking:

- (void)setImageWithURL:(NSURL *)url {
    [self setImageWithURL:url placeholderImage:nil];
}

- (void)setImageWithURL:(NSURL *)url 
       placeholderImage:(UIImage *)placeholderImage
{
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    [request setHTTPShouldHandleCookies:NO];
    [request addValue:@"image/*" forHTTPHeaderField:@"Accept"];

    [self setImageWithURLRequest:request placeholderImage:placeholderImage success:nil failure:nil];
}

- (void)setImageWithURLRequest:(NSURLRequest *)urlRequest 
              placeholderImage:(UIImage *)placeholderImage 
                       success:(void (^)(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image))success
                       failure:(void (^)(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error))failure
{
...
}

和SDWebImage

- (void)setImageWithURL:(NSURL *)url
{
    [self setImageWithURL:url placeholderImage:nil options:0 progress:nil completed:nil];
}

- (void)setImageWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholder
{
    [self setImageWithURL:url placeholderImage:placeholder options:0 progress:nil completed:nil];
}

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