How to not initialize part of a struct

Question

I want to combine what I think is called a grouped global with an embedded lock like this:

var stats struct {
    sync.RWMutex
    m map[string]statsEntry
}

Unfortunately for the map to be useful, it has to be made, so the code becomes:

var stats = struct {
  sync.RWMutex
  m map[string]statsEntry
}
{
  ???,
  make(map[string]statsEntry),
}

What to put instead of ????

Mr_Pink · Accepted Answer · 2016-05-24 20:44:56Z

6

You use a type literal:

stats := struct {
    sync.RWMutex
    m map[string]statsEntry
}{
    sync.RWMutex{},
    make(map[string]statsEntry),
}

But since the zero value of sync.RWMutex is valid, you can skip it and specify the fields you're assigning

stats := struct {
    sync.RWMutex
    m map[string]statsEntry
}{
    m: make(map[string]statsEntry),
}

But it's often just clearer to define the type locally

type s struct {
    sync.RWMutex
    m map[string]statsEntry
}

stats = s{m: make(map[string]statsEntry)}

answered May 24, 2016 at 20:25

Mr_Pink

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1 Comment

I always struggle finding type names for global variables because I read you shouldn't name them var something somethingType.