Modifying struct XML mappings for unmarshalling at runtime

<p>I&#39;m grabbing some XML data from a series of very similar, but not identical APIs and then unmarshalling it to golang structs. I basically want to make one struct to hold all the different types of responses. In order to do that, I think I need to modify the xml mappings at runtime. </p> <p>If I were to make separate types for each type of response it would look like:</p> <pre><code>type Response struct { Products []Product `xml:&#34;GetRedProducts&gt;Product&#34;` } type Response2 struct { Products []Product `xml:&#34;GetBlueProducts&gt;Product&#34;` } </code></pre> <p>This is a big pain. All the rest of the code is essentially the same. It&#39;s only the XML mapping that needs to change between different types.</p> <p>I want to do something like:</p> <pre><code>type Response struct { Products []Product Type: &#34;BlueProducts&#34; } </code></pre> <p>And then somehow infer the xml mapping at runtime from the Type. Is this a reasonable thing to be doing at all? Could someone show me how this works? Thanks :)</p> <hr/>**评论：**<br/><br/>tgulacsi: <pre><p>You can write your own unmarshaler using xml.Decoder, or use go1.8&#39;s new property of allowing assignment between same structs with different tags.</p></pre>theholeeric: <pre><p>I did not really want to write my own unmarshaller, but structs in 1.8 sound worth pursuing. TY</p></pre>TUSF: <pre><p>If you only want a single type for both APIs, you could give the type both fields, and during runtime check if one is empty?</p> <pre><code>type Response struct { RedProducts []Product `xml:&#34;GetRedProducts&gt;Product&#34;` BlueProducts []Product `xml:&#34;GetBlueProducts&gt;Product&#34;` } </code></pre> <p>This way you can infer the XML mapping by checking if <code>len(resp.RedProducts)</code> is 0 or not. Honestly, I think the Unmarshaler should have some kind of syntax to deal with multiple fields, but that&#39;s unfortunately not the case (Not as of 1.7.5, and neither does 1.8rc3).</p></pre>jerf: <pre><p>A general point about the decoders in the encoding library: they are quick, convenient decoders for when they work. However, it is simply unavoidable that sometimes you will have to write custom code. That&#39;s not really about Go per se, its just that the format&#39;s are too powerful to be convenient mapped anywhere, so a convenient mapping <strong>must</strong> also oversimplify, and combined with fact people do crazy things with these formats, you sometimes will have to do manual work. </p> <p>This is especially true when you get things like keys in JSON that have different JSON types, depending on the mod of the emitter. Or an array of heterogeneous types. Or tag soup in XML.</p></pre>