Append struct to anonymous slice of structs in Go

Question

I'm working with a defined struct such as this one:

type MyList struct { Items []struct { ResourceLocation string `json:"resourceLocation"` Resource Tmp `json:"resource"` } `json:"items"` ListOptions }

and I need to add a struct to Items slice.

I tried the following:

tmp2 := struct { ResourceLocation string Resource Tmp }{ Resource: myTempStruct, } tmpList.Items = append(MyList.Items, tmp)

but I'm getting a:

Cannot use 'tmp' (type struct {...}) as type struct {...}

error.

By the way, I cannot modify

type MyList struct { Items []struct { ResourceLocation string `json:"resourceLocation"` Resource Tmp `json:"resource"` } `json:"items"` ListOptions }

that's the reason why I cannot assign a name to Items and define it in a separate struct. Thanks.

You have to add the identical json tags as well to the anonymous struct. — Burak Serdar
– Burak Serdar, Commented Jul 17, 2020 at 2:29

score 3 · Accepted Answer · 2020-07-17 02:35:38Z

The code in the question does not work because field tags are part of the type.

Add the field tags to the anonymous type in the question:

item := struct { ResourceLocation string `json:"resourceLocation"` Resource Tmp `json:"resource"` }{ Resource: myTempStruct, }

Better yet, declare a type with same underlying type as an element of MyList.Items.

type Item struct { ResourceLocation string `json:"resourceLocation"` Resource Tmp `json:"resource"` }

Use that type when constructing the element:

item := Item{Resource: myTempStruct} list.Items = append(list.Items, item)

that worked like charm. Didn't know the field tags had to do with that, I thought they were only like decorative (for information purposes only). Thanks

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