英文:
Golang interfaces do not need to be imported?
问题
如果你看一下File结构体，它有一个Read()和Write()函数，与io.Writer和io.Reader接口的Read()和Write()函数完全相同。但是在File包中找不到io包（没有导入）。这是否意味着接口根本不需要导入就可以使用？只要Read()的定义与接口相同，就可以暗示它是io.Writer或io.Reader接口的一部分吗？
英文:
If you take a look at the File struct it has a Read() and Write() function that is exactly the same as io.Writer and io.Reader interface Read() and Write() functions. But the package io is no where to be found in File package (not imported). Does this mean that interfaces do not at all have to be imported to be used? As long as the Read() definition is the same as the interface it can then be implied that it is part of the io.Writer or io.Reader interface?
答案1
得分: 12
Package os does not import package io as the io.Reader interface is not used in package os.
The type *File happens to implement io.Reader because it has a Read method with the right signature. This implements relation is implicit and it is neither needed nor possible to make this explicit (e.g. like in Java with implements ISomeThing).
You asked: "Does this mean that interfaces do not at all have to be imported to be used?" and the formal answer is: Of course not! If you want to use io.Reader you have to import "io".
But implementing/satisfying an interface is not an use of this interface: Any type implements any interface (even future ones which have not been invented yet) just by having the right methods.
英文:
Package os does not import package io as the io.Reader interface is not used in package os.
The type *File happens to implement io.Reader because it has a Readmethod with the right signature. This implements relation is implicit and it is neither needed nor possible to make this explicite (e.g. like in Java with implements ISomeThing).
You asked: "Does this mean that interfaces do not at all have to be imported to be used?" and the formal answer is: Of course not! If you want to use io.Reader you have to import "io".
But implementing/satisfying an interface is not an use of this interface: Any type implements any interface (even future ones which have not been invented jet) just by having the right methods.
答案2
得分: 1
导出的实体是常量、变量和类型。要使用它们，即要引用这些导出的实体，必须使用它们的[限定]名称，而限定符是导出它们的包的基本名称。这也意味着要使用该包的导入语句。也就是说，在文件范围内绑定导出的实体是[严格]_显式_的。没有导入就无法访问导出的内容。
另一方面，实现接口是指定为_隐式_的：
> 一个类型实现了包含其方法的任何接口的任何子集，因此可以实现多个不同的接口。例如，所有类型都实现了空接口：
interface{}
英文:
Exported entities are constants, variables and types. To use them, ie. to refer to such exported entities, one has to use their [qualified] name, while the qualifier is the basename of the package which exports them. That also implies using an import statement of such package. IOW, binding exported entities in a file scope is [strictly] explicit. No import == no access to exported stuff.
OTOH, implementing an interface is specified to be implicit:
> A type implements any interface comprising any subset of its methods and may therefore implement several distinct interfaces. For instance, all types implement the empty interface:
interface{}
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