如何在Go中初始化组合结构？ [英] How do I initialize a composed struct in Go?

问题描述

  type Base结构{
 ID字符串
} 
 
类型子结构{
 Base $ b $ int int 
b int 
} 
  

当我初始化 Child 时，我无法初始化 ID 字段。

  //未知字段'ID'，类型为Child 
 child：= Child {ID：id，a：a，b：b} 
  

  child：= Child {a：23，b：42} 
 child.ID =foo
  

这似乎违反了封装。 Child的用户必须知道ID字段有些不同。如果我后来将一个公共字段移动到嵌入式结构中，那可能会破坏初始化。

我可以写一个 NewFoo（）方法，并希望每个人都使用它，但 是否有一种方法可以安全地使用结构体字面值，而嵌入式结构体不会显示某些字段被嵌入？ strong>还是我在这里应用了错误的模式？

解决方案

使用嵌套复合文字初始化单个表达式中的值： / b>

  child：= Child {Base：Base {ID：id}，a：a，b：b} 
  

无法隐藏从嵌入式结构中提升字段这一事实。

Let's say I have a struct with another struct embedded in it.

type Base struct {
    ID string
}

type Child struct {
    Base
    a int
    b int
}

When I go to initialize Child, I can't initialize the ID field directly.

// unknown field 'ID' in struct literal of type Child
child := Child{ ID: id, a: a, b: b }

I instead have to initialize the ID field separately.

child := Child{ a: 23, b: 42 }
child.ID = "foo"

This would seem to violate encapsulation. The user of Child has to know there's something different about the ID field. If I later moved a public field into an embedded struct, that might break initialization.

I could write a NewFoo() method for every struct and hope everyone uses that, but is there a way to use the struct literal safely with embedded structs that doesn't reveal some of the fields are embedded? Or am I applying the wrong pattern here?

解决方案

Use nested composite literals to initialize a value in a single expression:

child := Child{Base: Base{ID: id}, a: a, b: b}

It's not possible to hide the fact that a field is promoted from an embedded struct.

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