Question

当我构建我的应用程序时，我创建了一个名为NetEngine的类来管理所有网络请求。但我发现在我退出使用NetEngine的视图控制器之后，我仍然会调用成功或失败块。

的ViewController：

    [[NetEngine engine] GET:httpUrl success:^(id responseObject) {
         //some code here
         //It's still called after I quit viewctroller
    } failure:^(NSError *error) {
         //some code here
         //It's still called after I quit viewctroller
    }];

NetEngine：

typedef void(^SuccessBlock) (id responseObject);
typedef void(^FailureBlock) (NSError *error);

@interface NetEngine ()

@property (nonatomic, strong) AFHTTPSessionManager *httpManager;

@end

@implementation NetEngine

+ (NetEngine *)engine {
    static NetEngine *_sharedEngengine = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _sharedEngengine = [[self alloc] init];
    });

    return _sharedEngengine;
}

- (id)init {
    if (self = [super init]) {
        _httpManager = [[AFHTTPSessionManager alloc] initWithBaseURL:[NSURL URLWithString:BZTVBaseServerPath]];
        [_httpManager.requestSerializer setValue:@"application/json" forHTTPHeaderField:@"accept"];
        _httpManager.requestSerializer.cachePolicy = NSURLRequestReloadIgnoringLocalCacheData;
        _httpManager.operationQueue.maxConcurrentOperationCount = 4;
        [_httpManager.requestSerializer setTimeoutInterval:10.0];
    }
    return self;
}

- (void)GET:(NSString *)URLString success:(SuccessBlock)successBlock failure:(FailureBlock)failureBlock {
    // some thing about cache

    [_httpManager GET:encodeUrl parameters:nil success:^(NSURLSessionDataTask * _Nonnull task, id  _Nonnull responseObject) {
        [[self defaultCache] setObject:responseObject forKey:cacheKey];
        if (successBlock) {
            successBlock(responseObject);
        }
    } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
        if (isCache) {            
            if (successBlock) {
                successBlock([[self defaultCache] objectForKey:cacheKey]);
            }
        }
        if (failureBlock) {
            failureBlock(error);
        }
    }];
}

Answer 1

来自文档：＆＃34;块是添加到C，Objective-C和C ++的语言级功能，它允许您创建可以传递给方法或函数的不同代码段，就像它们一样值＆＃34 ;.因此，块本身就是一个对象，这意味着它的生命周期不依赖于创建它的对象。

如果您不希望NetEngine使用您提供给它的代码，那么当您退出时，您需要一种方法将该信息传递给它。视图控制器。

基本上：

[[NetEngine engine] GET:httpUrl success:^(id responseObject) {
    // if the view controller still wants me to do this {
       //some code here
    // }
} failure:^(NSError *error) {
    // if the view controller still wants me to do this {
       //some code here
    // }
}];

Answer 2

如果要在退出视图控制器时取消网络呼叫，请执行以下操作：

创建cancel BOOL变量

添加viewWillDisappear方法：

-(void) viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];

    cancel = YES;
}

检查回调方法中取消是否为

   [[NetEngine engine] GET:httpUrl success:^(id responseObject) {
         //some code here
         //It's still called after I quit viewctroller
         if (!cancel) {
            //do what you have to do
         }
    } failure:^(NSError *error) {
         //some code here
         //It's still called after I quit viewctroller
         if (!cancel) {
            //do what you have to do
         }
    }];

退出视图控制器后不要调用回调块

2 个答案: