Had same issue recently and worked around it using standard golang syntax
below
type mergeit struct {
One FirstStruct
Second SecondStruct
}
var finalmerge mergeit
then simply reference using
finalmerge.One = "blah blah blah"
On Monday, 21 November 2016 19:02:05 UTC, Howard C. Shaw III wrote:
>
> What is the intended use-case for this? Depending on the purpose, you
> might have a look at mergo, https://github.com/imdario/mergo as it does
> something similar, mostly for pulling configuration settings from multiple
> places and combining them with defaults.
>
> For JSON maps, there is https://github.com/peterbourgon/mergemap , and
> for simpler situations (i.e. merging JSON structs without merging embedded
> slices or maps), this solution https://play.golang.org/p/8jlJUbEJKf from
> rog in this post
> https://groups.google.com/forum/#!topic/golang-nuts/nLCy75zMlS8.
>
> As to the code itself, let's see...
>
> I do find it a little odd that when asked to merge A, and B, passed in
> that order, it returns B, A when both items are ints or strings, but if A
> is a slice, then B is appended to A's slice.
>
> So mergeDataStructures("A", "B") = ["B", "A"], while
> mergeDataStructures([]interface{}{"A"},"B") = ["A", "B"]
>
> Just looks like an accidental flipping of b and a to me, easily fixed.
>
> Meanwhile mergeDataStructures("A",[]interface{}{"B"}) panics. (i.e. case
> string: case []interface{}), and even if that code did work, it only
> references a, so it would be returning an incomplete result even if it did
> work.
>
> When handed two similar items on the same level - two strings or two ints
> or an int and a string, it promotes the return object to a slice, whereas
> when the same key with different values appears in two maps being merged,
> one overwrites the other instead of being promoted. It can't handle structs
> apparently at all (just a suggestion: many structs can be JSON marshaled
> and unmarshaled to an map[string]interface{}, which might let them be
> incorporated fairly simply).
>
> Moving on to the question of elegance:
>
> To my knowledge, there is no simpler way in Go to merge two maps other
> than to iterate over one, settings the keys and values into the other
> (obviously, the one being iterated over effectively has precedence,
> overwriting the corresponding values in the other). As to merging slices as
> you have done, well, that rather depends on the intended semantics, so I'm
> not sure you can do it generically without being wrong for at least some
> cases. After all, a slice in an arbitrary data structure or document might
> be sorted or unsorted, or it might be being used as a set and so need to
> reject duplicate items.
>
> So while it might need a few cases tweaked, I think in general you have a
> reasonably workable solution. I do see that this code does not handle
> hierarchical maps - it assigns all of a's map values to a map, then all of
> b's to the same map, without regard for whether they are duplicated.
>
> Howard
>
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