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?
Golang接口不需要导入吗?
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- douzongluo7542 2013-07-09 22:58关注
Package
os
does not import packageio
as theio.Reader
interface is not used in packageos
.The type
*File
happens to implementio.Reader
because it has aRead
method 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 withimplements 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 toimport "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.
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