iOS設置並在加載時獲取屬性

Question

我正在嘗試初始化加載視圖時從parse.com獲取的幾個屬性，以便可以對其進行計算。 例如，我在頭文件中聲明以下內容：

TaskViewController.h

@property (nonatomic, assign) int taskTotalCount;
@property (nonatomic, assign) int taskCompletedCount;
@property (nonatomic, assign) int progressCount;


- (void)CountAndSetTotalTask;
- (void)CountAndSetCompletedCount;
- (void)CalculateProgress;

然后在實現中，假設所有其他初始化都已正確設置，並在viewdidload中調用了它們，以下是方法的實現：

TaskViewController.m

- (void)CountAndSetCompletedCount {
    // Query the tasks objects that are marked completed and count them
    PFQuery *query = [PFQuery queryWithClassName:self.parseClassName];
    [query whereKey:@"Goal" equalTo:self.tasks];
    [query whereKey:@"completed" equalTo:[NSNumber numberWithBool:YES]];
    [query countObjectsInBackgroundWithBlock:^(int count, NSError *error) {
        if (!error) {

            // The count request succeeded. Assign it to taskCompletedCount
            self.taskCompletedCount = count;

            NSLog(@"total completed tasks for this goal = %d", self.taskCompletedCount);

        } else {
            NSLog(@"Fail to retrieve task count");
        }
    }];

}

- (void)CountAndSetTotalTask {
    // Count the number of total tasks for this goal
    PFQuery *query = [PFQuery queryWithClassName:self.parseClassName];
    [query whereKey:@"Goal" equalTo:self.tasks];
    [query countObjectsInBackgroundWithBlock:^(int count, NSError *error) {
        if (!error) {

            // The count request succeeded. Assign it to taskTotalCount
            self.taskTotalCount = count;

            NSLog(@"total tasks for this goal = %d", self.taskTotalCount);
        } else {
            NSLog(@"Fail to retrieve task count");
        }
    }];
}

- (void)CalculateProgress {
    int x = self.taskCompletedCount;
    int y = self.taskTotalCount;
    NSLog(@"the x value is %d", self.taskCompletedCount);
    NSLog(@"the y value is %d", self.taskTotalCount);
    if (!y==0) {
        self.progressCount = ceil(x/y); 
    } else {
        NSLog(@"one number is 0");
    }

    NSLog(@"The progress count is = %d", self.progressCount);
}

我遇到的問題是taskTotalCount和taskCompletedCount設置正確，並且在前兩個方法中返回不同的數字，而NSLog為x和y返回0。 因此，我不確定在設置兩個屬性之前是否以某種方式加載了第三個方法，還是其他一些問題。 預先感謝您提供任何指導。

Answer 1

假設您按以下方式調用這三種方法：

- (void)viewDidLoad {
    [super viewDidLoad];

    [self CountAndSetCompletedCount];
    [self CountAndSetTotalTask];
    [self CalculateProgress];
}

那么問題在於，前兩個方法會在后台調用Parse時立即返回。 這意味着在您從對Parse的調用中獲取結果之前很久就調用了CalculateProgress 。

一種解決方案是CountAndSetCompletedCount viewDidLoad調用CountAndSetCompletedCount 。 然后，在其完成處理程序中，調用CountAndSetTotalTask 。 最后，在其完成處理程序中調用CalculateProgress 。