How to Assign True to a Bool Pointer in Go Struct Literals?

Pointer Assignment in Struct Literals: A Concise Guide

In Go, assigning values to pointers within struct literals can be tricky. Specifically, setting a bool pointer to true can require a workaround.

Consider the following function that accepts a bool pointer:

import "fmt"

func main() {
    fmt.Println("Hello, playground")
    check(handler{is: new(bool)})
}

type handler struct{
    is *bool
}

func check(is handler){}

To assign the is field to true in the struct literal, one might assume a simple notation exists:

handler{is: &true}  // This is invalid

Unfortunately, this is not valid Go syntax. To set the bool pointer to true, a workaround is required.

Creating a Slice Wrapper

One method is to create a slice containing a single bool value of true and index its first element:

h := handler{is: &[]bool{true}[0]}
fmt.Println(*h.is) // Prints true

While this allows you to set the pointer to true, it unnecessarily creates a slice array that will remain in memory until the address to its first element is deleted.

Using Helper Functions

A cleaner solution is to create a helper function that returns a pointer to a bool variable initialized to true:

func newTrue() *bool {
    b := true
    return &b
}

This function can then be used in the struct literal:

h := handler{is: newTrue()}
fmt.Println(*h.is) // Prints true

Anonymous Functions and One-Liners

Other options to set the pointer to true include anonymous functions:

h := handler{is: func() *bool { b := true; return &b }()}
fmt.Println(*h.is) // Prints true

Or variant:

h := handler{is: func(b bool) *bool { return &b }(true)}

These allow for concise syntax but can be less readable than the helper function approach.

Conclusion

While setting a bool pointer to true in struct literals may seem like a simple task, it requires a specific syntax or the use of a workaround. Knowing these methods empowers Go programmers to effectively assign values to pointers in various situations.

The above is the detailed content of How to Assign True to a Bool Pointer in Go Struct Literals?. For more information, please follow other related articles on the PHP Chinese website!