Home > Backend Development > Golang > Why Doesn't Modifying a Go Struct's Field Within a Value Receiver Method Persist?

Why Doesn't Modifying a Go Struct's Field Within a Value Receiver Method Persist?

DDD
Release: 2024-12-13 03:17:13
Original
628 people have browsed it

Why Doesn't Modifying a Go Struct's Field Within a Value Receiver Method Persist?

Modifying Structs via Value Receivers: Understanding the Shadowing Effect

In Go, the behavior of method receivers can have a profound impact on the mutability of structs. Understanding the difference between value receivers and pointer receivers is crucial for manipulating structs correctly.

Problem Context

The example provided demonstrates a seemingly unexpected behavior. A struct's field is modified within a method, but the modification does not persist outside of the method.

type Test struct {
    someStrings []string
}

func (this Test) AddString(s string) {
    this.someStrings = append(this.someStrings, s)
    this.Count() // will print "1"
}

func (this Test) Count() {
    fmt.Println(len(this.someStrings))
}
Copy after login

When this code is executed, it prints:

1
0
Copy after login

This behavior arises because the AddString method uses a value receiver, which essentially creates a copy of the struct when the method is invoked. The modifications made within the method are applied to this copy, not the original struct. Consequently, when Count is invoked outside the method, it operates on the original, unmodified struct.

Pointer Receivers vs. Value Receivers

To resolve this issue, a pointer receiver must be used instead of a value receiver. Pointer receivers create a reference to the original struct, allowing for direct manipulation.

func (t *Test) AddString(s string) {
    t.someStrings = append(t.someStrings, s)
    t.Count() // will print "1"
}
Copy after login

With a pointer receiver, the AddString method operates directly on the receiver's struct. The modification to someStrings is thus reflected in the original struct. As a result, when Count is invoked outside the method, it operates on the modified struct.

Conclusion

By understanding the difference between value receivers and pointer receivers, you can effectively manipulate structs in Go. Value receivers create copies, while pointer receivers provide direct access to the original struct. This nuance is crucial for ensuring that changes made within methods are persistent outside of those methods.

The above is the detailed content of Why Doesn't Modifying a Go Struct's Field Within a Value Receiver Method Persist?. For more information, please follow other related articles on the PHP Chinese website!

source:php.cn
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Popular Tutorials
More>
Latest Downloads
More>
Web Effects
Website Source Code
Website Materials
Front End Template