英文:
Override AvailabilityZones (Function in Interface) in AWS CDK With Go
问题
Stack.AvailabilityZones的文档中写道：
// 要指定选择可用区的不同策略，请重写此方法。
AvailabilityZones() *[]*string
这是我尝试实现的代码：
stack := awscdk.NewStack(scope, &id, &sprops)
stack.AvailabilityZones = func() *[]*string { // 这是第22行
return &[]*string{jsii.String("us-west-1a")}
}
然而，我得到了错误：
[andrew@localhost cdk]$ go run vpc.go common.go
./vpc.go:22:2: cannot assign to stack.AvailabilityZones (value of type func() *[]*string)
我应该如何做才对？
我不确定我是否犯了一个愚蠢的错误，或者我是否需要完全不同的做法（在Go中，“override”是什么意思，它不是面向对象的？编辑：或者至少不是以一种我可以从Python示例中复制的方式）。
英文:
The documentation for Stack.AvailabilityZones says:
// To specify a different strategy for selecting availability zones override this method.
AvailabilityZones() *[]*string
This is my code that attempts to do this:
stack := awscdk.NewStack(scope, &id, &sprops)
stack.AvailabilityZones = func() *[]*string { // this is line 22
return &[]*string{jsii.String("us-west-1a")}
}
However, I get the error:
[andrew@localhost cdk]$ go run vpc.go common.go
./vpc.go:22:2: cannot assign to stack.AvailabilityZones (value of type func() *[]*string)
How should I be doing this?
I am not sure if I have made a stupid mistake or if I need to do something completely different (what does "override" mean in go which is not OO? edit: or at least not in a way that means I can copy from a python example).
答案1
得分: 1
Go有一种继承和“覆盖”方法的方式。你可以通过在结构体中“嵌入”另一个类型（不给类型命名）来实现继承；参考：https://stackoverflow.com/questions/21527489/go-inheritance-using-anonymous-type-in-a-struct-as-a-method-parameter
你的结构体将会继承嵌入类型的所有方法。你可以通过在结构体上直接声明方法来覆盖其中的某些方法。
一个简化的示例如下：
type MyStack struct {
awscdk.Stack
}
func (s *MyStack) AvailabilityZones() *[]string {
return &[]string{"foo", "bar"}
}
func f() {
// ...
stack := awscdk.NewStack(scope, &id, &sprops)
myStack := &MyStack{Stack: stack}
fmt.Println(myStack.AvailabilityZones())
}
编辑：以下是我（Andrew Cooke）实际测试通过的代码（但没有解决我的更大问题，所以没有进行深度测试）：
type ZoneStack struct {
awscdk.Stack
}
func (stack *ZoneStack) AvailabilityZones() *[]*string {
return &[]*string{jsii.String("us-west-1a")}
}
...
zstack := ZoneStack{}
awscdk.NewStack_Override(&zstack, scope, &id, &sprops)
（上面的原始答案可以编译，但会出现与JS序列化相关的运行时错误！）
英文:
Go has a way to inherit and "override" methods. You inherit by "embedding" another type inside a struct (where you don't name the type); see: https://stackoverflow.com/questions/21527489/go-inheritance-using-anonymous-type-in-a-struct-as-a-method-parameter
Your struct will then inherit all the methods from the embedded type.
And you can override individual ones by declaring them directly on the struct.
With a simplified example, that would look like:
type MyStack struct {
awscdk.Stack
}
func (s *MyStack) AvailabilityZones() *[]string {
return &[]string{"foo", "bar"}
}
func f() {
// ...
stack := awscdk.NewStack(scope, &id, &sprops)
myStack := &MyStack{Stack: stack}
fmt.Println(myStack.AvailabilityZones())
}
edit: this is what actually worked for me (andrew cooke) (but didn't solve my larger problem, so isn't deeply tested)
type ZoneStack struct {
awscdk.Stack
}
func (stack *ZoneStack) AvailabilityZones() *[]*string {
return &[]*string{jsii.String("us-west-1a")}
}
...
zstack := ZoneStack{}
awscdk.NewStack_Override(&zstack, scope, &id, &sprops)
(the original answer above compiles, but gives runtime errors that seem to be related to JS serialization?!)
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