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NSMutable数组在另一个方法中不返回值

nsmutablearray objective-c ios

Hanz Cheah · 技术社区 · 7 年前

我已经在一个方法中创建了一个NSMutable数组并将其添加到其中。下面是代码

-(void)setupSegmentButtons {

NSInteger numControllers = 7;

NSDate *now = [NSDate date];
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDate *beginningOfThisWeek;
NSTimeInterval durationOfWeek;

[calendar rangeOfUnit:NSWeekCalendarUnit
            startDate:&beginningOfThisWeek
             interval:&durationOfWeek
              forDate:now];

NSMutableArray *dtDate = [@[] mutableCopy];

NSDateComponents *comps = [calendar components:NSUIntegerMax fromDate:now];
NSDateFormatter *dateFormatter=[[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"dd/MM/YYYY"];

for (int i = 0; i<numControllers; i++) {

    UIButton *button = [[UIButton alloc]initWithFrame:CGRectMake(X_BUFFER+i*(self.view.frame.size.width-2*X_BUFFER)/numControllers-X_OFFSET, Y_BUFFER, (self.view.frame.size.width-2*X_BUFFER)/numControllers, HEIGHT)];

    [navigationView addSubview:button];

    NSString *dateString = [dateFormatter stringFromDate:[calendar dateFromComponents:comps]];

    [dtDate addObject:dateString];

    [button addTarget:self action:@selector(tapSegmentButtonAction:) forControlEvents:UIControlEventTouchUpInside];

    ++comps.day;
}

//****** Manage to display my array with all the dates
NSLog(@" Can get my array : %@",dtDate);

}

但当按下按钮并调用下面的另一个方法时,NSMutable数组dtDate返回(null),为什么?

-(void)tapSegmentButtonAction:(UIButton *)button {

//Can't get the NSMutable Array here 
NSLog(@" Returns Null : %@",dtDate);

NSString *txtDate = dtDate[0];
//Returns NULL
NSLog(@"txtDate=%@",txtDate);
}

4 回复 | 直到 7 年前

CRD 7 年前

您的方法 tapSegmentButtonAction: 访问权限 dtDate 没有任何声明,指示它是实例或全局变量。

您的方法 setupSegmentButtons 声明变量 dtDate日期 创建一个局部变量,该变量隐藏具有相同名称的任何实例或全局变量。

而不是:

NSMutableArray *dtDate = [@[] mutableCopy];

您应该尝试:

dtDate = [NSMutableArray new];

HTH公司

Akhil 7 年前

dtDate是方法中的局部变量。。

如果您有用于存储dtDate变量的属性

您应该执行

self.yourProperty = dtDate

Nilesh Jha 7 年前

//将其作为全局变量写入

NSMutableArray *dtDate;

-(void)setupSegmentButtons {

NSInteger numControllers = 7;

NSDate *now = [NSDate date];
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDate *beginningOfThisWeek;
NSTimeInterval durationOfWeek;

[calendar rangeOfUnit:NSWeekCalendarUnit
            startDate:&beginningOfThisWeek
             interval:&durationOfWeek
              forDate:now];

dtDate = [NSMutableArray alloc] init];

NSDateComponents *comps = [calendar components:NSUIntegerMax fromDate:now];
NSDateFormatter *dateFormatter=[[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"dd/MM/YYYY"];

for (int i = 0; i<numControllers; i++) {

    UIButton *button = [[UIButton alloc]initWithFrame:CGRectMake(X_BUFFER+i*(self.view.frame.size.width-2*X_BUFFER)/numControllers-X_OFFSET, Y_BUFFER, (self.view.frame.size.width-2*X_BUFFER)/numControllers, HEIGHT)];

    [navigationView addSubview:button];

    NSString *dateString = [dateFormatter stringFromDate:[calendar dateFromComponents:comps]];

    [dtDate addObject:dateString];
    NSLog(@"dtDate inside loop =%@",dtDate);// for checking wheter at ths instance You have value or not
    button.tag = i;

    [button addTarget:self action:@selector(tapSegmentButtonAction:) forControlEvents:UIControlEventTouchUpInside];

    ++comps.day;
}

//****** Manage to display my array with all the dates
NSLog(@" Can get my array : %@",dtDate);

}

-(void)tapSegmentButtonAction:(UIButton *)button {

//Can't get the NSMutable Array here 
NSLog(@" Returns Null : %@",dtDate);

NSString *txtDate = dtDateArray[0];
//Returns NULL
NSLog(@"txtDate=%@",txtDate);
}

Hanz Cheah 7 年前

在我将NSMutable数组放在viewDidLoad之后,它就变成了全局数组

- (void)viewDidLoad
{
[super viewDidLoad];

dtDate = [[NSMutableArray alloc] init];
}

我真的不明白为什么,如果有人能解释的话,那就太好了。