golang中关键字var之后的下划线和接口名称是什么意思？ [英] what does a underscore and interface name after keyword var in golang mean?

问题描述

http://golang.org/src/pkg/database/sql/driver/types.go

30  type ValueConverter interface {
31      // ConvertValue converts a value to a driver Value.
32      ConvertValue(v interface{}) (Value, error)
33  }

54  var Bool boolType
55  
56  type boolType struct{}
57  
58  var _ ValueConverter = boolType{}
59  
60  func (boolType) String() string { return "Bool" }
61  
62  func (boolType) ConvertValue(src interface{}) (Value, error) {....}

如上所述，我知道ValueConverter是一个接口名称，第58行似乎是声明boolType实现接口ValueConverter，这是否有必要？我删除了第58行，代码运行良好

As above, I known that ValueConverter is an interface name, line 58 seems like to declare that boolType implement interface ValueConverter, does that necessary? I deleted line 58, the code works well

推荐答案

它提供了一个静态（编译时）检查 boolType 满足 ValueConverter 界面。用作变量名称的 _ 告诉编译器有效地丢弃RHS值，但是如果它有任何副作用，则进行类型检查并评估它，但是匿名变量本身不占用任何进程空间。

It provides a static (compile time) check that boolType satisfies the ValueConverter interface. The _ used as a name of the variable tells the compiler to effectively discard the RHS value, but to type-check it and evaluate it if it has any side effects, but the anonymous variable per se doesn't take any process space.

这是一个方便的构造，当开发时，接口的方法集和/或类型实现的方法经常改变。该构造可以作为防止忘记匹配类型和接口的方法集合的意图，其目的是让它们兼容。它有效地防止去安装一个有这种省略的破碎（中间）版本。

It is a handy construct when developing and the method set of an interface and/or the methods implemented by a type are frequently changed. The construct serves as a guard against forgetting to match the method sets of a type and of an interface where the intent is to have them compatible. It effectively prevents to go install a broken (intermediate) version with such omission.

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