ios - 构建 queryString 时 NSURLComponents 出现问题

Question

我收到这个错误:

-[__NSCFNumber stringByAddingPercentEncodingWithAllowedCharacters:]: unrecognized selector sent to instance 0x7fab88c21750        

我用这段代码得到它:

+ (NSString *)queryStringFromDictionary:(NSDictionary *)queryDictionary
{
    NSURLComponents *components = [NSURLComponents componentsWithString:@""];
    NSMutableArray *urlQueryComponents = [NSMutableArray array];

    for (NSString *key in [queryDictionary allKeys])
    {
        NSString *value = queryDictionary[key];
        NSURLQueryItem *newQueryItem = [NSURLQueryItem queryItemWithName:key value:value];
        [urlQueryComponents addObject:newQueryItem];
    }

    components.queryItems = urlQueryComponents; // HERE I GET THE ERROR
    return [components query];
}

在出现错误的情况下，我的 queryDictionary 看起来像这样:

{
    lat = "49.3437442";
    lng = "17.0571453";
    username = demo;
}

还有一次，当我的 queryDictionary 如下所示时，它工作正常!

{
    latlng = "49.343744,17.057145";
    sensor = true;
}

所以我不明白这个问题或我该如何解决它。有什么想法吗？

Answer 1

你正在传递一个包含 NSNumber 作为键或值的字典。 queryWithItem:value: 期望键和值都是字符串。

选项 1

解决此问题的最简单方法是将所有键/值视为 NSObject 并使用 stringWithFormat 将它们转换为字符串。

替换:

NSURLQueryItem *newQueryItem = [NSURLQueryItem queryItemWithName:key value:value];

与:

NSURLQueryItem *newQueryItem = [NSURLQueryItem queryItemWithName:[NSString stringWithFormat:@"%@", key] value:[NSString stringWithFormat:@"%@", value]];

选项 2

如果你想坚持所有键都是字符串，我建议你使用泛型来输入字典，如果找到非字符串键则使用 NSAssert(这样你就可以找到你当前的错误)。

+ (NSString *)queryStringFromDictionary:(NSDictionary <NSString*, NSString*> *)queryDictionary {
    NSURLComponents *components = [NSURLComponents componentsWithString:@""];
    NSMutableArray *urlQueryComponents = [NSMutableArray array];

    for (NSString *key in [queryDictionary allKeys]) {
        NSString *value = queryDictionary[key];

        // confirm key/value are strings
        NSAssert([key isKindOfClass:[NSString class]], @"keys must be strings!");
        NSAssert([value isKindOfClass:[NSString class]], @"values must be strings!");

        NSURLQueryItem *newQueryItem = [NSURLQueryItem queryItemWithName:key value:value];
        [urlQueryComponents addObject:newQueryItem];
    }

    components.queryItems = urlQueryComponents;
    return [components query];
}