How do struct{} and struct{}{} work in Go?

Question

I am wondering what does "struct{}" and "struct{}{}" mean in Go? An example is as follows: array[index] = struct{}{} or make(map[type]struct{})

Gopher · Accepted Answer

struct is a keyword in Go. It is used to define struct types, which is a sequence of named elements. For example: type Person struct { Name string Age int } The struct{} is a struct type with zero elements. It is often used when no information is to be stored. It has the benefit of being 0-sized, so usually no memory is required to store a value of type struct{}. struct{}{} on the other hand is a composite literal, it constructs a value of type struct{}. A composite literal constructs values for types such as structs, arrays, maps and slices. Its syntax is the type followed by the elements in braces. Since the "empty" struct (struct{}) has no fields, the elements list is also empty: struct{} {} | ^ | ^ type empty element list As an example let's create a "set" in Go. Go does not have a builtin set data structure, but it has a builtin map. We can use a map as a set, as a map can only have at most one entry with a given key. And since we want to only store keys (elements) in the map, we may choose the map value type to be struct{}. A map with string elements:

Go Language

Similar Questions

How to check a channel is closed or not before reading it?

How to Initialize array of structs in Go?

How to decleare constant struct in Go ?

On a mission to build Next-Gen Community Platform for Developers

Facebook

Twitter

Linkedin

Instagram