How Do Underscore-Named Empty Struct Fields Enforce Keyed Field Assignment in Go?

Enforcing Keyed Fields with Underscore-Named Empty Struct Fields

In Go, you may encounter code that utilizes a seemingly peculiar field named with an underscore (_) containing an empty struct.

type SomeType struct {
  Field1 string
  Field2 bool
  _      struct{}
}

This technique plays a crucial role in enforcing keyed fields when declaring structs. Consider the following:

type SomeType struct {
  Field1 string
  Field2 bool
  _      struct{}
}

// Only keyed fields are permitted:
bar := SomeType{Field1: "hello", Field2: true}

// Compile error:
foo := SomeType{"hello", true}

By using an underscore-named empty struct field, you can ensure that all fields within a struct must be specified by their corresponding field names. This becomes especially useful when extending the struct in the future to avoid breaking existing code that assumes keyed field assignment.

Essentially, the underscore-named empty struct field serves as a placeholder to enforce keyed fields, contributing to the robustness and maintainability of Go code.

The above is the detailed content of How Do Underscore-Named Empty Struct Fields Enforce Keyed Field Assignment in Go?. For more information, please follow other related articles on the PHP Chinese website!