Learn X By Example
Learn X By Example

    Go by Example: Methods

    Go by Example : Methods

    Go supports methods defined on struct types.

    package main
    import "fmt"
    type rect struct {
    width, height int
}

    This area method has a receiver type of *rect .

    func (r *rect) area() int {
    return r.width * r.height
}

    Methods can be defined for either pointer or value receiver types. Here’s an example of a value receiver.

    func (r rect) perim() int {
    return 2*r.width + 2*r.height
}
    func main() {
    r := rect{width: 10, height: 5}

    Here we call the 2 methods defined for our struct.

        fmt.Println("area: ", r.area())
    fmt.Println("perim:", r.perim())

    Go automatically handles conversion between values and pointers for method calls. You may want to use a pointer receiver type to avoid copying on method calls or to allow the method to mutate the receiving struct.

        rp := &r
    fmt.Println("area: ", rp.area())
    fmt.Println("perim:", rp.perim())
}
    $ go run methods.go 
area:  50
perim: 30
area:  50
perim: 30

    Next we’ll look at Go’s mechanism for grouping and naming related sets of methods: interfaces.

    Next example: Interfaces .

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