doutou7549 2018-07-20 22:08
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Go中具有动态类型(空接口)的XML Unmarshal

I need to parse an XML message that has a dynamic element, so I have used an element of type interface{} to represent it in my Message struct.

Once I know the type of this dynamic element (at runtime) I initialise a message struct and then try to unmarshal the XML message. However, the contents of the dynamic element are not unmarshalled.

Here is a Go Playground with what I'm trying to achieve, with comments and the actual vs expected outputs: https://play.golang.org/p/eKVetUPmVI2

I tried several variations but can't get the unmarshalling to work as expected. Can anyone help me to understand why this behaviour and how to make it work? Thanks in advance.

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  • duanbai1974 2018-07-21 03:03
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    Per the encoding/xml package documentation:

    If the XML element contains a sub-element that hasn't matched any of the above rules and the struct has a field with tag ",any", unmarshal maps the sub-element to that struct field.

    One small update to your code makes it work as you expected:

    Add the xml:",any" tag to your Other field definition.

    To clean up the code, I would also remove the Any type, you don't need it. You can change the Other field definition to type interface{} with tag xml:",any" and accomplish the same thing.

    Like so:

    Other interface{} `xml:",any"`
    

    Execute and see the "1000" captured.

    I suggest updating your question to include your code directly to make it easier for people to find/search/read your question. Having the Go playground link as well is also useful so readers can quickly run/tweak/test the example.

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