Obj-C→递增一个数字（并在Cocoa标签上显示步骤） [英] Obj-C -> Incrementing a number (and showing steps on a Cocoa label)

问题描述

我是Objective-C的新手，所以可能有一个简单的解决方案。

I'm new with Objective-C, so there probably is a simple solution to this.

我想要一个数字递增，但每次迭代显示在标签上。 （例如，它显示1，2，3，4，5 ...显示分开的时间量）。

I want a number to increment, but each iteration to be show on a label. (for example, it shows 1, 2, 3, 4, 5... displayed apart by an amount of time).

我试过：

#import "testNums.h"

@implementation testNums
- (IBAction)start:(id)sender {
    int i;
    for(i = 0; i < 10; ++i)
    {
        [outputNum setIntValue:i];
        sleep(1);
    }
}
@end

等待9秒（显然冻结），然后在文本框中显示9。

and all it did was wait for 9 seconds (apparently frozen) and then displayed 9 in the text box.

推荐答案

消息，请使用 NSTimer 或延迟执行。这是后者：

To allow the run loop to run between messages, use an NSTimer or delayed perform. Here's the latter:

- (IBAction) start:(id)sender {
    [self performSelector:@selector(updateTextFieldWithNumber:) withObject:[NSNumber numberWithInt:0] afterDelay:1.0];
}

- (void) updateTextFieldWithNumber:(NSNumber *)num {
    int i = [num intValue];
    [outputField setIntValue:i];
    if (i < 10)
        [self performSelector:@selector(updateTextFieldWithNumber:) withObject:[NSNumber numberWithInt:++i] afterDelay:1.0];
}

这里有一个基于定时器的解决方案。你可能会发现它更容易遵循。您可以从文本字段中设置文本字段的值：

Here's one timer-based solution. You may find it easier to follow. You could set the text field's value from the text field:

@interface TestNums: NSObject
{
    IBOutlet NSTextField *outputField;
    NSTimer *timer;
    int currentNumber;
}

@end

@implementation TestNums

- (IBAction) start:(id)sender {
    timer = [[NSTimer scheduledTimerWithTimeInterval:1.0
        target:self
        selector:@selector(updateTextField:)
        userInfo:nil
        repeats:YES] retain];

    //Set the field's value immediately to 0
    currentNumber = 0;
    [outputField setIntValue:currentNumber];
}

- (void) updateTextField:(NSTimer *)timer {
    [outputField setIntValue:++currentNumber];
}

@end

）基于定时器的解决方案，使用属性。您需要在Interface Builder中将文本字段绑定到属性（选择字段，按⌘4，选择对象，然后输入 currentNumber 作为键绑定）。

Here's an even better (cleaner) timer-based solution, using a property. You'll need to bind the text field to the property in Interface Builder (select the field, press ⌘4, choose your object, and enter currentNumber as the key to bind to).

@interface TestNums: NSObject
{
    //NOTE: No outlet this time.
    NSTimer *timer;
    int currentNumber;
}

@property int currentNumber;

@end

@implementation TestNums

@synthesize currentNumber;

- (IBAction) start:(id)sender {
    timer = [[NSTimer scheduledTimerWithTimeInterval:1.0
        target:self
        selector:@selector(updateTextField:)
        userInfo:nil
        repeats:YES] retain];

    //Set the field's value immediately to 0
    self.currentNumber = 0;
}

- (void) updateTextField:(NSTimer *)timer {
    self.currentNumber = ++currentNumber;
}

@end

基于属性的解决方案至少有两个优点：

The property-based solution has at least two advantages:

1. 你的对象不需要知道文本字段。 （它是一个模型对象，与文本字段的视图对象分开。）


2. 要添加更多文本字段，只需在IB中创建和绑定它们。您不必向TestNums类中添加任何代码。

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