Question

How can to initialize any fields in golang types? For example:

type MyType struct {
    Field string = "default" 
}

Answer 1

You can't have "default" values like that, you can either create a default "constructor" function that will return the defaults or simply assume that an empty / zero value is the "default".

type MyType struct {
    Field string
} 

func New(fld string) *MyType {
    return &MyType{Field: fld}
}

func Default() *MyType {
    return &MyType{Field: "default"}
}

Also I highly recommend going through Effective Go.

Answer 2

There is no way to do that directly. The common pattern is to provide a New method that initializes your fields:

func NewMyType() *MyType {
    myType := &MyType{}
    myType.Field = "default"
    return myType

    // If no special logic is needed
    // return &myType{"default"}
}

Alternatively, you can return a non-pointer type. Finally, if you can work it out you should make the zero values of your struct sensible defaults so that no special constructor is needed.

How to initialize struct fields

2 个答案: