将项目添加到块内的NSMutableArray中时遇到问题 [英] Trouble with adding item into an NSMutableArray inside a block

问题描述

更新: 我刚刚发现了一个棘手的部分...如果我做这样的事情，它会起作用:

UPDATE: I just found a tricky part... if I do something like this, it works:

[_friendsArrayInBlock insertObject:@"Bla" atIndex:itemIndex];

但不是:

[_friendsArrayInBlock insertObject:friend atIndex:itemIndex];

为什么我不能添加自定义对象，但是可以添加NSString?有什么问题

Why I cannot add a custom object, but I can add NSString? What's the problem

原始部分: 在这里，您可以看到相关的代码部分:

ORIGINAL PART: Here you can see the relevant code part:

@implementation ORGFriendsTableViewController
{
    NSMutableArray *_friendsArray;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    _friendsArray = [NSMutableArray array];
    __block NSMutableArray *_friendsArrayInBlock = _friendsArray;

    [FBRequestConnection startForMyFriendsWithCompletionHandler: ^(FBRequestConnection *connection,
                                                                   id result,
                                                                   NSError *error) {
        FBGraphObject *fbGraphObject = (FBGraphObject *)result;

        NSMutableArray *userArray = fbGraphObject[@"data"];
        for (FBGraphObject *user in userArray) {

            ORGFBUser *friend = [[ORGFBUser alloc] initWithId:user[@"id"] name:user[@"name"] andPhotoURL:@"someurl"];

            NSInteger itemIndex = 0;
            [_friendsArrayInBlock insertObject:friend atIndex:itemIndex];
            [self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:[NSIndexPath indexPathForItem:itemIndex inSection:0]] withRowAnimation:UITableViewRowAnimationRight];
        }
    }];
}

此行出现问题:

[_friendsArrayInBlock insertObject:friend atIndex:itemIndex];

程序接收信号"EXC_BAD_ACCESS"

Program recieving signal "EXC_BAD_ACCESS"

我认为它与块概念有关，并从中更改了非线程安全的NSMutableArray.

I think it's related with block concept, and altering a non thread-safe NSMutableArray from it.

您知道如何解决此问题吗?

Do you have any idea how to fix this?

推荐答案

块无需使用__block即可访问实例变量(请参见

Blocks can access instance variables without using __block (see this). Therefore this should work:

- (void)viewDidLoad
{
    [super viewDidLoad];

    _friendsArray = [NSMutableArray array];

    [FBRequestConnection startForMyFriendsWithCompletionHandler: ^(FBRequestConnection *connection,
                                                                   id result,
                                                                   NSError *error) {
        FBGraphObject *fbGraphObject = (FBGraphObject *)result;

        NSMutableArray *userArray = fbGraphObject[@"data"];
        for (FBGraphObject *user in userArray) {

            ORGFBUser *friend = [[ORGFBUser alloc] initWithId:user[@"id"] name:user[@"name"] andPhotoURL:@"someurl"];

            NSInteger itemIndex = 0;
            [_friendsArray insertObject:friend atIndex:itemIndex];
            [self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:[NSIndexPath indexPathForItem:itemIndex inSection:0]] withRowAnimation:UITableViewRowAnimationRight];
        }
    }];
}

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