Solve golang error: invalid receiver type 'x' ('x' is not a defined type), solution

Solution to golang error: invalid receiver type 'x' ('x' is not a defined type), solution

In the process of using Golang programming, we often You will encounter various errors. One of the common errors is "invalid receiver type 'x' ('x' is not a defined type)". This error message means that we used an undefined type as the receiver when declaring the method. In this article, I'll show you how to solve this problem and provide corresponding code examples.

When the above error occurs, first we need to check whether the receiver type in the code is correctly defined. The receiver type is the type that precedes the parameter list in the method declaration. We need to make sure that the receiver type is a defined type and not a non-existent type.

Let us look at a sample code:

package main

import "fmt"

type Point struct {
    X int
    Y int
}

func (p Point) Print() {
    fmt.Printf("Point coordinates: (%d, %d)
", p.X, p.Y)
}

func main() {
    p := Point{X: 1, Y: 2}
    p.Print()
}

The above code defines a structure named Point and defines a Print method for it. In the Print method, we use the Point type as the receiver type. In this way, we can call the Print method through a variable of type Point to print the coordinates of the point.

However, if we mistakenly use an undefined type as the receiver type in the code, it will cause an "invalid receiver type" error. Let's look at a modified code example:

package main

import "fmt"

type Point struct {
    X int
    Y int
}

type Polygon []Point

func (p Polygon) Print() {
    for _, point := range p {
        fmt.Printf("Polygon point coordinates: (%d, %d)
", point.X, point.Y)
    }
}

func main() {
    poly := Polygon{{X: 1, Y: 2}, {X: 3, Y: 4}, {X: 5, Y: 6}}
    poly.Print()
}

In the modified code, we define a Polygon type, which is a slice of Point. Then we try to use the Polygon type as the receiver type of the Print method. Since the Polygon type is defined by ourselves and has not been defined by the standard library or elsewhere, the compiler will report an error "invalid receiver type 'Polygon' ('Polygon' is not a defined type)".

In order to solve this problem, we need to change the receiver type to an already defined type. For example, we can change the receiver type to a pointer to the Polygon type:

func (p *Polygon) Print() {
    for _, point := range *p {
        fmt.Printf("Polygon point coordinates: (%d, %d)
", point.X, point.Y)
    }
}

Modify like this Finally, we can successfully compile and run the code without the "invalid receiver type" error.

Summary:
To solve the "invalid receiver type 'x' ('x' is not a defined type)" error in golang, you need to check whether the receiver type in the code is correctly defined. If the receiver type is an undefined type, it needs to be modified to a defined type. In general, changing the receiver type to a pointer to that type is a common solution. By analyzing the cause of the error and making modifications according to the actual situation, we can easily solve this problem.

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