我对Objective-C还是很陌生，必须从@property (strong, nonatomic) NSMutableArray *allCategories块中的AFHTTPRequestOperationManager内部动态更改success的值。
在循环中，[self.allCategories addObject:tempObject];不会更改allCategories的值。
该变量已在viewDidLoad中初始化为self.allCategories = [[NSMutableArray alloc]init];。
我还尝试在启动__block NSMutableArray *tempCategories = [[NSMutableArray alloc]init];对象之前将临时变量创建为AFHTTPRequestOperationManager。 tempCategories甚至不保留其值。无法弄清发生了什么.EditSorry给您带来不便viewDidLoad包含以下代码-(NSMutableArray *)loadData
{
__block NSMutableArray *tempCategories = [[NSMutableArray alloc]init];
manager = [AFHTTPRequestOperationManager manager];
[manager GET:kAPICategoryList
parameters:nil
success:^(AFHTTPRequestOperation *operation, id responseObject) {
// downcast id to NSMutableDictionary
NSMutableDictionary *json = (NSMutableDictionary *)responseObject;
// check if dictionary is non nil has at least 1 element
if (json != nil && [json count] >= 1) {
// NSLog(@"json:\t%@", json);
// check json is non nil & has success message
if ([json objectForKey:kAPIKeyCategoryRoot] != nil) {
NSArray *arrCategoriesRoot = [json objectForKey:kAPIKeyCategoryRoot];
// check categories has some data
if (arrCategoriesRoot.count >= 1) {
for (int i = 0; i < arrCategoriesRoot.count; i++) {
SomeModel *pCategory;
NSDictionary *dctCategorySingle = [arrCategoriesRoot objectAtIndex:i];
// check category has sub category
if ([dctCategorySingle objectForKey:kAPIKeyCategorySubCategory] != nil) {
// create category with sub category
pCategory = [[SomeModel alloc]initWithSubCategorisedCategoryID:[dctCategorySingle objectForKey:kAPIKeyCategoryID]
name:[dctCategorySingle objectForKey:kAPIKeyCategoryName]
image:kIMGCategoryDefault
subCategory:[dctCategorySingle objectForKey:kAPIKeyCategorySubCategory]];
} else{
// create just a category
pCategory = [[SomeModel alloc]initWithCategoryID:[dctCategorySingle objectForKey:kAPIKeyCategoryID]
name:[dctCategorySingle objectForKey:kAPIKeyCategoryName]
image:kIMGCategoryDefault];
} // else just
[tempCategories addObject:pCategory];
[_allCategories addObject:pCategory];
} // for
NSLog(@"categories count %lu", [self.allCategories count]);
} // if count >= 1
}
else if ([json objectForKey:kAPIRespMsgCategoryFetchErrKey] != nil) {
[Utility showAlertWithTitle:kAPIRespMsgCategoryFetchErrKey
message:[json objectForKey:kAPIRespMsgCategoryFetchErrVal]
button:kMsgButtonOkayTtl];
}
} else {
// error in login => enable login
NSLog(@"%@", kMsgNetworkEmptyJSON);
}
}
// network error
failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(@"error %@", [error localizedDescription]);
}];
NSLog(@"tempCategories count %lu", [tempCategories count]);
return tempCategories;
}
这是NSLog：2015-03-19 18：27：17.845 MyProject [4011：121268] viewDidLoad的输出形式
2015-03-19 18：27：18.133 MyProject [4011：121268] tempCategories计数0
2015-03-19 18：27：18.136 MyProject [4011：121268] numberOfRowsInSection计数0
2015-03-19 18：27：18.137 MyProject [4011：121268] numberOfRowsInSection计数0
2015-03-19 18：27：19.019 MyProject [4011：121268]当self.allCategories = [[NSMutableArray alloc]init];完成allCategories时，类别计数为20（无）。
最佳答案
据我所知，它应该以这种方式工作..在确定allCategories的内容之前，您确定成功调用了成功块吗？
成功块以异步方式工作，这意味着仅在RequestOperation完成时才执行（如果下载较大的文件可能会花费很长时间）
如果尝试在执行成功块之前获取allCategories的值，则不会获得期望的结果。我建议您在成功块上使用断点或NSLog来查看它是否已在您认为正在执行时执行。
例如
...
successBlock:^(AFHTTPRequestOperation *operation, id responseObject)
{
NSLog(@"Success");
[self.allCategories addObject:tempObject]
}]; //End of request
[operation start]; //Begin executing the AFHTTPOperation
NSLog("%@",self.allCategories.description); //probably nil or empty
//since the success block hasn't been called yet
编辑：
就像我一样，您正在返回一个由异步操作设置的before值，要从异步操作返回一个值，我建议您看一下answer和this一个。另外，您还应该阅读一下异步任务的工作原理。
基本上，您要对异步操作/任务执行的操作是确保该值在您要使用时可用。这样做的主要问题是您不知道何时设置该值，但是可以确保在设置该值后要执行的操作。
为此，您可以创建一个带有自定义完成块的简单方法
- (void)myCustomMethodWithCompletionBlock: (void (^)(NSArray *))completion {
//Do your request
//...
successBlock:^(AFHTTPRequestOperation *operation, id responseObject)
{
NSLog(@"Success");
completionBlock(allCategories);
}]; //End of request
}
同时，在您的主要方法中，您调用
[self myCustomMethodWithCompletionBlock:^(NSArray *allCategories) {
self.allCategories = allCategories;
//Do other stuff you need to with that variable since now you are
//sure the value will be set unless the operation failed
}];
关于ios - 如何从块内部修改非局部(全局)变量？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/29143998/