performSelector可能导致泄漏，因为其选择器未知IN Singleton Class / FUNCTION Pointer -Passing Function作为参数

Question

@interface URLClass : NSObject
{
    id target;
    SEL funObj;
}
+ (URLClass *)sharedInstance;
-(void)theBigFunction:(SEL)func :(id)target;
@property (nonatomic,retain) SEL funObj;

#import "URLClass.h"

static URLClass *instance = NULL;


@implementation URLClass
{
    NSMutableData *webData;
}
- (id)init
{
    if ( self = [super init] )
    {

    }
    return self;    
}

+ (URLClass *)sharedInstance
{
    @synchronized([URLClass class])
    {
        if (!instance)
            instance = [[super alloc] init];        
        return instance;
    }    
    return nil;
}
-(void)theBigFunction:(SEL)func :(id)targetObj{

    funObj =func;
    target=targetObj;  
    NSURL *URL = [NSURL URLWithString:@"urlString"];    
    NSURLRequest *request = [NSURLRequest requestWithURL:URL];
    NSURLConnection *connection = [NSURLConnection connectionWithRequest:request delegate:self];

    if( connection )
    {
        webData = [NSMutableData data] ;
    }
    else
    {
        NSLog(@"theConnection is NULL");
    }
}



-(BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)protectionSpace
{

    return YES;
}
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [webData setLength: 0];
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [webData appendData:data];
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{    
    NSLog(@"ERROR with theConenction");
}
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{    

    NSError *error;
    id jsonObj = [NSJSONSerialization JSONObjectWithData:webData options:0 error:&error];    
    if (jsonObj!=nil && error==nil) {        
        if ([jsonObj isKindOfClass:[NSDictionary class]]) {            
            NSDictionary *dic=(NSDictionary*)jsonObj;
            NSLog(@"DIC jsonObj %@ ",dic);
            NSArray *array=[dic objectForKey:@"items"];
            NSLog(@"array jsonObj %@  %d",array,[array count]);
        }else if ([jsonObj isKindOfClass:[NSArray class]]) {

            NSArray *arr=(NSArray*)jsonObj;
            NSLog(@"arr jsonObj %@ ",arr);
        }
    }
    [target performSelector:funObj];
// Not gEtting called the aboue line

// performSelector可能会导致泄漏，因为它的选择器是上面行中的未知警告}

当我计划执行下面的行形式来自任何类的代码。 它不被称为。

-(void)loginPress:(id)sender{
    URLClass *rlOBJ=[URLClass sharedInstance];   
    [rlOBJ theBigFunction:@selector(upd_Handler:) :self];
}
- (void) upd_Handler: (id) value{

    NSLog( @"Seccess");    
}

Answer 1

现代方法是让您的类接受完成块而不是目标/选择器。 然后你不必插入一堆丑陋的编译器抑制行，你就会获得更大的灵活性。

Answer 2

以下是[target performSelector:selector withObject:object];完全替换[target performSelector:selector withObject:object]; 避免警告。 使用这样的替换之一：

[NSObject target:target performSelector:selector withObject:object];

@interface NSObject (NSPerformSelector)

+ (id)target:(id)target performSelector:(SEL)selector;
+ (id)target:(id)target performSelector:(SEL)selector withObject:(id)object;
+ (id)target:(id)target performSelector:(SEL)selector withObject:(id)object1 withObject2:(id)object2;

@end

@implementation NSObject (NSPerformSelector)

+ (id)target:(id)target performSelector:(SEL)selector {

    IMP imp = [target methodForSelector:selector];
    id (*func)(id, SEL) = (void *)imp;
    return func(target, selector);
}

+ (id)target:(id)target performSelector:(SEL)selector withObject:(id)object {

    IMP imp = [target methodForSelector:selector];
    id (*func)(id, SEL, id) = (void *)imp;
    return func(target, selector, object);
}

+ (id)target:(id)target performSelector:(SEL)selector withObject:(id)object1 withObject2:(id)object2 {

    IMP imp = [target methodForSelector:selector];
    id (*func)(id, SEL, id, id) = (void *)imp;
    return func(target, selector, object1, object2);
}

@end

Answer 3

只需使用[sender performSelector:selector withObject:object afterDelay:0]; 这将删除警告，代码将运行正常。

Answer 4

这是一个警告，而不是错误。 你的代码应该仍然有效。

当您调用选择器并且编译器无法判断选择器是什么时，它无法判断被调用的方法是否将获取传递的对象的所有权，或者释放它，或者其他什么。 因此ARC无法确定将正确处理参数的内存管理。

您应该能够在编译器指令中包含performSelector调用以禁用该警告。 然后，您将负担确保被调用的方法不会对传递给它的对象保持任何强引用，或释放该对象。

Answer 5

您不需要在bigFunction中传递成功方法。 相反，你应该使用完成块，如[Wil Shipley] [1]所建议的那样

以下是NSURLConnection发出异步请求并返回的示例; 响应，数据和错误; 如果有的话。 将来你应该参考文档。

NSURLConnection类参考https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSURLConnection_Class/index.html

+ (void)sendAsynchronousRequest:(NSURLRequest *)request
                      queue:(NSOperationQueue *)queue
          completionHandler:(void (^)(NSURLResponse *response,
                                      NSData *data,
                                      NSError *connectionError))handler

你可以像这样重写你的bigFunction方法 -

- (void)bigFunctionWithYourInputData:(NSDictionary*)userInfo withCompletionHandler:(void(^)(NSData* data, NSError* error))completionHandler {
    NSURL *theUrl = [NSURL URLWithString:[userInfo objectForKey:@"url"];
    NSURLRequest *req = [NSURLRequest requestWithURL:theUrl];
   [NSURLConnection sendAsynchronousRequest:req queue:nil completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {

        if (!connectionError) {
            //do what you want with your data
            NSLog(@"response :%@", response);
            NSLog(@"data     :%@", data);

            //pass to your completion handler
            if(completionHandler) {
                completionHandler(data, nil);
            }
        } else {
            //something went wrong
            NSLog(@"Got the error with code :%ld", (long)connectionError.code);

            //pass to your completion handler
            if(completionHandler) {
                completionHandler(nil, error);
            }
        }
    }];
}

然后你会通过你的单身人士在其他地方实现它 -

[URLClass sharedInstance] bigFunctionWithYourInputData:_someDictionaryData withCompletionHandler:^(NSData* data, NSError* error) {

     if (!error) {
         //success
         NSLog(@"returned the data:%@", data);

     } else {

         //handler the error somehow
     }
 }];