删除所有以某个单词开头的NSUserDefaults [英] Delete all my NSUserDefaults that start with a certain word
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问题描述
我有没有办法在我的iPhone应用程序中遍历所有 NSUserDefault
的列表,只删除某些?
Is there a way for me to "walk" through a list of all the NSUserDefault
s in my iPhone app, and only delete certain ones?
例如,我想得到所有以某个单词开头的关键名称。
For example, I'd like to get all the key names that start with a certain word.
这样的事情:
[[NSUserDefaults standardUserDefaults] removeObjectForKey:@"Dog*"];
推荐答案
你可以查看 dictionaryRepresentation
。
You can look through the dictionaryRepresentation
.
这是一个使用 NSPredicate
作为通用匹配器以获得更大的灵活性。
Here's an implementation which uses NSPredicate
as a generic matcher for greater flexibility.
@interface NSUserDefaults (JRAdditions)
- (void)removeObjectsWithKeysMatchingPredicate:(NSPredicate *)predicate;
@end
@implementation NSUserDefaults (JRAdditions)
- (void)removeObjectsWithKeysMatchingPredicate:(NSPredicate *)predicate {
NSArray *keys = [[self dictionaryRepresentation] allKeys];
for(NSString *key in keys) {
if([predicate evaluateWithObject:key]) {
[self removeObjectForKey:key];
}
}
}
@end
用法:
NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF BEGINSWITH %@", @"something"];
[[NSUserDefaults standardUserDefaults] removeObjectsWithKeysMatchingPredicate:pred];
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