Question

//
//  ParkMeterViewController.h

@interface ParkMeterViewController : UIViewController <UIAlertViewDelegate>

{
    BOOL meterPickerIsDisplayed;
    BOOL reminderPickerIsDisplayed;
}

然后在.m文件中

//
//  ParkMeterViewController.m

- (void)extendRetractPicker:(UIDatePicker *)picker
                   andLabel:(UILabel*)label
                withPickerY:(int)pickerY
                  andLabelY:(int)labelY
             withDisplayVar:(id)isDisplayed
              andDisplaySet:(BOOL)status    {

    [UIView animateWithDuration:.5
                          delay:0
                        options:UIViewAnimationOptionCurveEaseInOut
                     animations:^{
                         picker.center = CGPointMake(picker.frame.origin.x + (picker.frame.size.width/2), pickerY);
                         label.center = CGPointMake(label.frame.origin.x + (label.frame.size.width/2), labelY);
                     }
                     completion:nil];

    isDisplayed = status;
}




//call for the method
 if (reminderPickerIsDisplayed == NO) {

    [self extendRetractPicker:reminderTimePicker andLabel:closeReminderLabel withPickerY:435 andLabelY:314 withDisplayVar:reminderPickerIsDisplayed andDisplaySet:YES];

}

基本上我试图让方法声明中的isDisplayed变量成为需要更改的BOOL变量名，然后将状态作为该BOOL的新状态。

Answer 1

您尝试实现的目标可以通过更改方法调用来完成 - 例如：

if (reminderPickerIsDisplayed == NO) {

    [self extendRetractPicker:reminderTimePicker andLabel:closeReminderLabel withPickerY:435 andLabelY:314];
    reminderPickerIsDisplayed=YES;

}

或者您可以将extendRetractPicker方法更改为

- (BOOL)extendRetractPicker:(UIDatePicker *)picker
                   andLabel:(UILabel*)label
                withPickerY:(int)pickerY
                  andLabelY:(int)labelY
             isDisplayed:(BOOL)isDisplayed    {

    [UIView animateWithDuration:.5
                          delay:0
                        options:UIViewAnimationOptionCurveEaseInOut
                     animations:^{
                         picker.center = CGPointMake(picker.frame.origin.x + (picker.frame.size.width/2), pickerY);
                         label.center = CGPointMake(label.frame.origin.x + (label.frame.size.width/2), labelY);
                     }
                     completion:nil];

   return !isDisplayed;
}

然后你的调用只是

reminderPickerIsDisplayed = [self extendRetractPicker:reminderTimePicker andLabel:closeReminderLabel withPickerY:435 andLabelY:314 isDisplayed:reminderPickerIsDisplayed];

Answer 2

这只是展示了使用下划线字符启动所有实例变量的重要性，因为每个有一点Objective-C经验的人都会告诉你。您显然确信您已将BOOL参数“status”分配给BOOL实例变量“meterPickerIsDisplayed”或“reminderPickerIsDisplayed”（我不知道哪一个），因此确信您将编译器错误消息归因于一些奇怪的事情。你无法理解，而实际上你试图将BOOL参数“status”分配给id参数“isDisplayed”。即使它是合法的，也没有任何意义。

它还显示了使用合理变量名称的重要性。为什么“withDisplayVar：（id）isDisplayed”？ isDisplayed是如何命名BOOL变量的。它应该被称为“idToDisplay”或类似的东西。然后，如果你试图分配

idToDisplay = status;

你已经发现这看起来不对劲了。

ARC不允许将'BOOL'（又名'signed char'）隐式转换为'id'

2 个答案: