iOS - NSUserDefaults 值为“valueForKey"返回 null 但不为 null [英] iOS - NSUserDefaults value returns null for 'valueForKey' but isn't null

问题描述

我试图通过检索每个产品标识符的 NSUserDefaults 值来查看用户是否进行了购买.我在购买产品并正确设置时保存该值.

I am trying to see if a user has made a purchase by retrieving the NSUserDefaults value for each product identifier. I save the value when a product is purchased and it is getting set correctly.

键值对在调用时正确显示:

NSLog(@"%@", [[NSUserDefaults standardUserDefaults] dictionaryRepresentation]);

这样:

"com.COMPANY.PRODUCTIDENTIFIER" = 1;

但是当我尝试实际验证该特定键值时，它总是返回 null:

    for (NSString * productIdentifier in _productIdentifiers) {
        NSLog(@"ProductIdentifier: %@",productIdentifier);
        NSLog(@"Defaults Value: %@",[[NSUserDefaults standardUserDefaults] valueForKey:productIdentifier]);
        NSLog(@"Defaults Bool: %d",[[NSUserDefaults standardUserDefaults] boolForKey:productIdentifier]);
        NSLog(@"Defaults Object: %@",[[NSUserDefaults standardUserDefaults] objectForKey:productIdentifier]);
        BOOL productPurchased = [[NSUserDefaults standardUserDefaults] boolForKey:productIdentifier];
        if (productPurchased) {
            [_purchasedProductIdentifiers addObject:productIdentifier];
            NSLog(@"Previously purchased: %@", productIdentifier);
        } else {
            NSLog(@"Not purchased: %@", productIdentifier);
        }
    }

结果如下:

2013-03-10 17:45:13.609 COMPANY[1140:907] ProductIdentifier:  com.COMPANY.PRODUCTIDENTIFIER
2013-03-10 17:45:13.611 COMPANY[1140:907] Defaults Value: (null)
2013-03-10 17:45:13.612 COMPANY[1140:907] Defaults Bool: 0
2013-03-10 17:45:13.611 COMPANY[1140:907] Defaults Object: (null)   

注意 - 上述方法均按此顺序在同一方法中调用，因此应用程序尚未加载默认值或其他类似内容都不是问题，因为该值已通过 ' 正确显示字典表示法.此外，公司和产品标识符已被替换为隐私.真正的应用程序中没有错别字，所以这不是问题.

更新

好的，这很有趣.如果我使用静态字符串作为键，它会返回正确的值.但是使用'productIdentifier'(它是NSString)不会，即使记录'productIdentifier'它是完全相同的字符串......有什么想法吗???

Ok so this is interesting. If I use a static string as the key, it returns the correct value. But using the 'productIdentifier' (which is NSString) does not, even though logging the 'productIdentifier' it is the exact same string... Any Ideas???

代码:

    for (NSString *productIdentifier in _productIdentifiers) {
        NSLog(@"ProductIdentifier: %@",productIdentifier);
        NSLog(@"Defaults Value: %@",[[NSUserDefaults standardUserDefaults] valueForKey:productIdentifier]);
        NSLog(@"Defaults Bool: %d",[[NSUserDefaults standardUserDefaults] boolForKey:productIdentifier]);
        NSLog(@"Defaults Object: %@",[[NSUserDefaults standardUserDefaults] objectForKey:productIdentifier]);
        NSLog(@"Static Key: %d",[[NSUserDefaults standardUserDefaults] boolForKey:@"com.COMPANY.PRODUCTIDENTIFIER"]);
        BOOL productPurchased = [[NSUserDefaults standardUserDefaults] boolForKey:productIdentifier];
        if (productPurchased) {
            [_purchasedProductIdentifiers addObject:productIdentifier];
            NSLog(@"Previously purchased: %@", productIdentifier);
        } else {
            NSLog(@"Not purchased: %@", productIdentifier);
        }
    }

结果:

2013-03-10 17:45:13.609 COMPANY[1140:907] ProductIdentifier:  com.COMPANY.PRODUCTIDENTIFIER
2013-03-10 17:45:13.611 COMPANY[1140:907] Defaults Value: (null)
2013-03-10 17:45:13.612 COMPANY[1140:907] Defaults Bool: 0
2013-03-10 17:45:13.611 COMPANY[1140:907] Defaults Object: (null)   
2013-03-10 17:45:13.611 COMPANY[1140:907] Static Key: 1   

推荐答案

问题在于您使用了 valueForKey: 而不是 objectForKey:.valueForKey 具有不同的语义(键值编码)，尤其是与包含点的键一起使用时.

The problem is your use of valueForKey: instead of objectForKey:. valueForKey has different semantics (key-value coding), especially when used with a key that has dots in it.

改变这个:

[[NSUserDefaults standardUserDefaults] valueForKey:productIdentifier]

为此:

[[NSUserDefaults standardUserDefaults] objectForKey:productIdentifier]

它应该可以工作.

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