Question

我正在制作我的第一个完成块，由于某种原因，它无法识别返回类型，因此我无法将值传递回方法调用。

继承我的标题声明

+(void)downloadVenues:(void (^)(NSArray *myVenues, NSError *error))block;

继承我的实施

+(void)downloadVenues:(void (^)(NSArray *myVenues, NSError *error))block{


//download scenes
PFQuery *query = [PFQuery queryWithClassName:@"Venues"];
[query orderByDescending:@"createdAt"];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if (error) {
        NSLog(@"Error: %@ %@", error, [error userInfo]);
    }
    else {
        // We found messages!
        myVenues = objects;


        NSLog(@"Retrieved %lu messages", (unsigned long)[myVenues count]);




    }
}];

并且他在另一个文件中调用它

//download venues
[Venue downloadVenues:^(NSArray *myVenues, NSError *error){
    if (error) {
        NSLog(@"Error: %@ %@", error, [error userInfo]);
    }
    else {

    NSLog(@"myObjects are: %@", myVenues);
    _venues = myVenues;

    [self loadAnnotations];

    }
}];

由于某种原因，它没有在实现中识别myVenues。为什么以及如何解决这个问题？感谢

Answer 1

您的实现永远不会调用完成块。这是你应该做的：

+(void)downloadVenues:(void (^)(NSArray *myVenues, NSError *error))block{


//download scenes
PFQuery *query = [PFQuery queryWithClassName:@"Venues"];
[query orderByDescending:@"createdAt"];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
    if (error) {
        NSLog(@"Error: %@ %@", error, [error userInfo]);
        block(nil, error);
    }
    else {
        // We found messages!
        block(objects, nil);


        NSLog(@"Retrieved %lu messages", (unsigned long)[myVenues count]);




    }
}];

完成块返回类型无法识别

1 个答案: