我发现自己使用以下模式作为在 Go 结构构造函数中获取具有默认值的可选参数的方法:
package main
import (
"fmt"
)
type Object struct {
Type int
Name string
}
func NewObject(obj *Object) *Object {
if obj == nil {
obj = &Object{}
}
// Type has a default of 1
if obj.Type == 0 {
obj.Type = 1
}
return obj
}
func main() {
// create object with Name="foo" and Type=1
obj1 := NewObject(&Object{Name: "foo"})
fmt.Println(obj1)
// create object with Name="" and Type=1
obj2 := NewObject(nil)
fmt.Println(obj2)
// create object with Name="bar" and Type=2
obj3 := NewObject(&Object{Type: 2, Name: "foo"})
fmt.Println(obj3)
}
是否有更好的方法允许使用默认值的可选参数?
最佳答案
Dave Cheney 提供了一个很好的解决方案,您可以使用功能选项来覆盖默认值:
https://dave.cheney.net/2014/10/17/functional-options-for-friendly-apis
所以你的代码会变成:
package main
import (
"fmt"
)
type Object struct {
Type int
Name string
}
func NewObject(options ...func(*Object)) *Object {
// Setup object with defaults
obj := &Object{Type: 1}
// Apply options if there are any
for _, option := range options {
option(obj)
}
return obj
}
func WithName(name string) func(*Object) {
return func(obj *Object) {
obj.Name = name
}
}
func WithType(newType int) func(*Object) {
return func(obj *Object) {
obj.Type = newType
}
}
func main() {
// create object with Name="foo" and Type=1
obj1 := NewObject(WithName("foo"))
fmt.Println(obj1)
// create object with Name="" and Type=1
obj2 := NewObject()
fmt.Println(obj2)
// create object with Name="bar" and Type=2
obj3 := NewObject(WithType(2), WithName("foo"))
fmt.Println(obj3)
}
关于constructor - Go 结构构造函数中具有默认值的可选参数,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/20150628/