从NSDictionary获取包含NSNumber bools的键列表,其值为@YES

Question

我正在尝试获取一组键,其中a中相应键的NSDictionary值为@ YES.

对于EG,:Starting Dictionary:

NSDictionary* dict = @{@"key1" : @YES, @"key2": @YES, @"key3": @NO, @"key4": @NO};

期望的结果:

NSArray* array = @[@"key1", @"key2"];

我尝试用NSPredicates和subpredicates做这个,但找不到一个做我想要的.我的"工作"但丑陋的解决方案是:

NSMutableArray* array = [[NSMutableArray alloc] initWithCapacity:0];
NSDictionary* dict = @{@"key1" : @YES, @"key2": @YES, @"key3": @NO, @"key4": @NO};
for (NSString* key in [dict allKeys]) {
    if ([[dict objectForKey:key] isEqualToNumber:@YES])
        [array addObject:key];
}

什么是更好的方法,可能与NSPredicates？

Answer 1

这种抽象的东西很多

NSArray *results = [dict keysOfEntriesPassingTest:^(id key, id obj, BOOL *stop) {
  return [obj isEqualToNumber:@YES];
}].allObjects;

NSLog(@"%@", results);