如何知道是否存在 NSUserDefault？

发布于 2024-11-05 05:06:17 字数 669 浏览 2 评论 0原文

我用什么条件才能知道我使用的 NSUserDefaults ？

NSUserDefaults *preftest;
preftest=[NSUserDefaults standardUserDefaults];
NSString *opening = [preftest stringForKey:@"opening"];

这就是我获取数据的方式。如果前缀 stringForKey:@"opening" 尚不存在，我想进入 if 条件......所以我尝试了：

if (opening == nil) {
    ...
    NSUserDefaults *pref = [NSUserDefaults standardUserDefaults];
    [pref setObject:@"OK" forKey:@"pass"];
    NSString *finalfr = [pref stringForKey:@"opening"];
    NSLog(@"(here's the new value of opening: %@ )", finalfr);
    ...
}

if (opening != nil) {
    NSLog(@" != nil");
    // http request}

但事实上，它不起作用。

谢谢你帮我！！

原文

What condition do I use to know it the NSUserDefaults I use?

NSUserDefaults *preftest;
preftest=[NSUserDefaults standardUserDefaults];
NSString *opening = [preftest stringForKey:@"opening"];

This is the way I'm getting the datas. I want to get into the if condition if the preftext stringForKey:@"opening" doesn't already exist.... So I tried :

if (opening == nil) {
    ...
    NSUserDefaults *pref = [NSUserDefaults standardUserDefaults];
    [pref setObject:@"OK" forKey:@"pass"];
    NSString *finalfr = [pref stringForKey:@"opening"];
    NSLog(@"(here's the new value of opening: %@ )", finalfr);
    ...
}

if (opening != nil) {
    NSLog(@" != nil");
    // http request}

But inded, it doesn't work.

Thanks to help me !!

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萌无敌 2024-11-12 05:06:17

我想进入if条件if
前缀 stringForKey:@"opening"
不已经存在......

但是您正在使用opening != nil测试它是否存在。
如果你想测试它是否不存在，则可以是 opening == nil 或只是 !opening。

NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
NSString *opening = [prefs stringForKey:@"opening"];

if (!opening) {
    [prefs setObject:@"OK" forKey:@"opening"];
    opening = [prefs stringForKey:@"opening"];
    NSLog(@"(here's the new value of opening: %@ )", opening);
    // prints: (here's the new value of opening: OK )
}

I want to get into the if condition if
the preftext stringForKey:@"opening"
doesn't already exist....

But you are testing if it does exist with opening != nil.
If you want to test if it does NOT exist, it would be opening == nil or just !opening.

NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
NSString *opening = [prefs stringForKey:@"opening"];

if (!opening) {
    [prefs setObject:@"OK" forKey:@"opening"];
    opening = [prefs stringForKey:@"opening"];
    NSLog(@"(here's the new value of opening: %@ )", opening);
    // prints: (here's the new value of opening: OK )
}

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