使用RxJava映射到映射

I know how to transform Map<X, Y> to Map<X, Z> using stream and it there was also a previous question about this.

我知道如何将Map 转换成Map 使用流，还有一个之前的问题。 ,> ,>

But I want to learn how do it using RxJava.

但是我想学习如何使用RxJava。

And to be more specific:

更具体地说:

//Input: 
Map<String,String> in; // map from key to a string number, for example: "10"

//transform: in -> out

//Output:
Map<String,Integer> out; //map from the same key to Integer.parseInt(val) (invariant: val is a string number)

2 个解决方案

#1

You can use Observable.toMap.

您可以使用Observable.toMap。

I think this is a minimal example:

我认为这是一个最小的例子:

Map<String, String> test = new HashMap<String, String>() {

    {
        put("1", "1");
        put("2", "2");
    }
};
Map<String, Integer> res = Observable.from(test.entrySet()).toMap(e -> e.getKey(), e -> Integer.parseInt(e.getValue())).toBlocking().first();

#2

I think Dávid Karnok is right in a sense that it is not particularly useful case for RxJava if your only goal is to convert a single map. It might make more sense if you have Observable of (multiple) maps.

我认为David Karnok的观点是对的，如果你的唯一目标是转换一个地图，那么对于RxJava就不是特别有用的。如果你能观察到(多个)地图，可能会更有意义。

Then I would recommend to use a convenience of Guava transformers: https://google.github.io/guava/releases/snapshot/api/docs/com/google/common/collect/Maps.html#transformValues(java.util.Map,%20com.google.common.base.Function)

然后，我建议使用方便的番石榴变压器:https://google.github.io/guava/releases/snapshot/api/docs/com/google/common/collect/Maps.html#transformValues(java.util.Map，% 20com.common.base.function)

Map<String,String> source1 = ...
Map<String,String> source2 = ...

Observable.just(source1, source2)
    .map(map->Maps.transformValues(map, v->Integer.parseInt(v)));

One nice thing about Guava's map value transformer is that it does not recreate map data structure, but instead creates a transformed view which maps values lazily (on the fly).

番石榴的映射值转换器的一个好处是，它不重新创建映射数据结构，而是创建一个转换后的视图，该视图缓慢地(动态地)映射值。

If you do not want to depend on Guava, you can just trivially implement Func1<Map<String,String>,Map<String,Integer>> yourself.

如果您不想依赖于番石榴，您可以简单地实现Func1 ，Map >。 ,integer>

#1