使用Mantle将JSON数组中的NSString转换为NSURL [英] Transform NSString to NSURL within a JSON Array with Mantle

问题描述

让我说的是以下JSON响应

Let's say given to me is the following JSON response

{
    "images": [
        "http://domain.com/image1.jpg",
        "http://domain.com/image2.jpg",
        "http://domain.com/image3.jpg"
    ]
}

我想使用Mantle解析这些字符串并将其转换为NSURL，但将其保留在NSArray中.

With Mantle I want to parse those strings and transform them into NSURLs but keep them in an NSArray.

所以我的Objective-C模型对象看起来像

So my Objective-C model object would look like

@interface MyModel : MTLModel <MTLJSONSerializing>
// Contains NSURLs, no NSStrings
@property (nonatomic, copy, readonly) NSArray *images;
@end

是否有一种优雅的方法来实现这一目标?一些NSURL数组转换器?

Is there an elegant way to achieve that? Some NSURL array transformer?

+ (NSValueTransformer*)imagesJSONTransformer
{
    return [NSValueTransformer mtl_JSONArrayTransformerWithModelClass:[NSURL class]];
}

很显然，NSURL不是从MTLModel派生的，所以这是行不通的.

Obviously NSURL does not derive from MTLModel, so that will not work.

推荐答案

不幸的是，Mantle 1.x没有简单的方法将现有的转换器(在本例中为名为MTLURLValueTransformerName的转换器)应用到数组.

Unfortunately, Mantle 1.x doesn't have an easy way to apply an existing transformer (in this case, the transformer named MTLURLValueTransformerName) to each element of an array.

您可以这样做:

+ (NSValueTransformer*)imagesJSONTransformer {
    NSValueTransformer *transformer = [NSValueTransformer valueTransformerForName:MTLURLValueTransformerName];
    return [MTLValueTransformer transformerWithBlock: ^NSArray *(NSArray *values) {
        NSMutableArray *transformedValues = [NSMutableArray arrayWithCapacity:values.count];
        for (NSString *value in values) {
            id transformedValue = [transformer transformedValue:value];
            if (transformedValue) {
                [transformedValues addObject:transformedValue];
            }
        }
        return transformedValues;
    }];
}

在Mantle 2.0中，您将可以使用预定义的数组映射转换器. Mantle 2.0仍在开发中.

In Mantle 2.0, you'll be able to use the predefined array mapping transformer. Mantle 2.0 is still in development.

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