Create JSON array from seperate []byte results in GoLang

Question

I have a loop of results coming from a tiedot query.

In it's most basic form it looks like this:

col.ForEachDoc(func(id int, docContent []byte) (willMoveOn bool) {
    return true
    return false
})

I can send these results down the pipe to the client, but only 1 at a time. Not quite what I want.

I can also create single JSON objects, using json.Unmarshal but how do I combine them all into 1 large JSON array?

Many thanks. New to GO!

It's a bit unclear what you mean with JSON array. Do you mean an array you can index, where each element is a dictionary, or do you mean a text json representation? — Per Johansson
– Per Johansson, Commented Oct 29, 2015 at 15:04

jmaloney · Accepted Answer · 2015-10-29 15:33:09Z

2

If you are returning this directly to the client and your docContent is JSON you can just manually construct the array syntax. It does not provide any safety if docContent is not valid json.

a := [][]byte{}

col.ForEachDoc(func(id int, docContent []byte) (willMoveOn bool) {
     a = append(a, docContent)
     return true
})
b := bytes.Join(a, []byte(`,`))

// insert '[' to the front
b = append(b, 0)
copy(b[1:], b[0:])
b[0] = byte('[')

// append ']'
b = append(b, ']')

You could also unmarshal, then append to a slice, then marshal the slice

s := []interface{}{}
col.ForEachDoc(func(id int, docContent []byte) (willMoveOn bool) {
     var j interface{}
     if err := json.Unmarshal(docContent, &j); err != nil {
          // handle error
     }
     s = append(s, j)
     return true
})

b, err := json.Marshal(j)

answered Oct 29, 2015 at 15:33

jmaloney

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