[英]iOS change Integer/NSNumber of parent ViewController
I have a viewController with a property of NSInteger (or NSNumber), What I want to do is pass the integer to the child ViewController, do some change (maybe add by some number). 我有一个具有NSInteger(或NSNumber)属性的viewController,我想要做的是将整数传递给子ViewController,做一些更改(可能添加一些数字)。
But when I use NSNumber as property in the parent and child controller and pass it by set property: 但是当我在父控制器和子控制器中使用NSNumber作为属性并通过set属性传递它时:
//parent and child property.
@property (nonatomic,strong) NSNumber *num;
//pass to the child
child.num = self.num;
//do some change in child
self.num = [NSNumber numberWithInteger:[self.num integerValue] + 1];
This cannot change the value of the parent , because NSNumber is readonly and in the child they alloc a new one, without change the value of the parent. 这不能更改父级的值,因为NSNumber是只读的,并且在子级中它们分配了一个新的,而不更改父级的值。
So: 所以:
How I can pass a NSInteger or NSNumber to the child ViewController and change the value in it, and when child is pop away, the parent controller get the change? 我如何将NSInteger或NSNumber传递给子ViewController并更改其中的值,当子弹出时,父控制器得到更改?
You are defining and assigning a new NSNumber in the following line: 您正在以下行中定义和分配新的NSNumber:
self.num = [NSNumber numberWithInteger:[self.num integerValue] + 1];
You can't use this method because NSNumbers are immutable. 您不能使用此方法,因为NSNumbers是不可变的。 So self.num will point to another location different from parent's
num
. 所以self.num将指向与父的
num
不同的另一个位置。 To avoid problems like this you can use delegate pattern or simply passing parent's viewController pointer to the child and changing its num
value. 为了避免这样的问题,你可以使用委托模式或简单地将父的viewController指针传递给子节点并更改其
num
值。
For example: 例如:
Parent's Header: 家长的标题:
@property (nonatomic,strong) NSNumber *num;
Child's Header: 孩子的标题:
@property (nonatomic,weak) parentViewControllerClass * parentClass;
Code: 码:
self.parentClass.num = [NSNumber numberWithInteger:[self.parentClass.num integerValue] + 1];
PS You can check out how to define protocols here and here . PS您可以在这里和这里查看如何定义协议。 With that you can implement the delegate pattern.
有了它,您可以实现委托模式。
Maybe in other language you could pass pointer to pointer (I'm not sure if you should ), but in Objective-C you can't request address of property. 也许在其他语言中你可以将指针传递给指针(我不确定你是否应该 ),但在Objective-C中你不能请求属性的地址。
What you can do is: 你可以做的是:
setNumber:
setNumber:
方法的协议setNumber:
setNumber:
function) setNumber:
function) setNumber:
from child controller setNumber:
来自子控制器 Create mutable object that is shared between parent and child controller. 创建父控制器和子控制器之间共享的可变对象。 For example:
例如:
@interface Counter : NSObject @property (nonatomic) NSInteger value; @end
You could post notification about number change from child controller and observe it in parent: 您可以从子控制器发布有关号码更改的通知,并在父级中观察它:
// post notification in child NSNumber *num = [NSNumber numberWithInteger:1]; [[NSNotificationCenter defaultCenter] postNotificationName:@"numberChangedNotification" object:self userInfo:@{@"number": num}]; // observe notifications in parent // first register observer in viewDidLoad [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(changeNumber:) name:@"numberChangedNotification" object:child]; // and implement updateNumber - changeNumber: (NSNotification *)notification { NSNumber *num = notification.userInfo[@"number"]; // ... }
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