如何检查 nsdictionary 键是否有值？

Question

我正在使用以下代码

 for(NSDictionary* key in [Tags valueForKey:@"data"]) {
                if ([[key valueForKey:@"hashtag"] rangeOfString:self.searchKey options:NSCaseInsensitiveSearch].location != NSNotFound) {
                    NSLog(@"found key");
}
break;
}

对于 nsdictionary

我不想使用 for 循环来检查第一个键值是否存在。实际上我只是想检查字典中是否返回了主题标签，或者只使用 if 语句。这怎么可能？

Answer 1

您可以使用谓词搜索带主题标签的标签：

        // MARK: - Without Loop
        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"hashtag != NULL"];
        NSArray *hashtaggedTags = [tags filteredArrayUsingPredicate:predicate];

        if (hashtaggedTags.count == 0) {
            NSLog(@"No hashtags at all");
        } else {
            NSLog(@"Found some hashtags");
        }

正在清理您的代码以获取最小可用代码：

int main(int argc, const char * argv[]) {
    @autoreleasepool {

        // Assuming you have some dictionary like this
        NSDictionary * Tags = @{
            @"data": @[ // <- Here is the array
                @{ // <- here is the dictionary
                    @"hashtag": @"NightOut",
                    @"count"  : @0,
                }
            ]
        };

        // Getting the tag value
        NSArray* tags = Tags[@"data"];

        // MARK: - Without Loop
        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"hashtag != NULL"];
        NSArray *hashtaggedTags = [tags filteredArrayUsingPredicate:predicate];

        if (hashtaggedTags.count == 0) {
            NSLog(@"No hashtags at all");
        } else {
            NSLog(@"Found some hashtags");
        }

        // MARK: - With loop
        // Loop through tags (not keys of the dictionary)
        for (NSDictionary * tag in tags) {
            // Check if `hashtag` is exists and returns something in the dictionary or not
            if (tag[@"hashtag"]) {
                NSLog(@"There's an object set for key @\"hashtag\"!");
            } else {
                NSLog(@"No object set for key @\"hashtag\"");
            }
        }
    }
    return 0;
}

如何检查 nsdictionary 键是否有值？

How to check if a nsdictionary key has values or not?

objective-c

ios