英文:
Error when calling interface function?
问题
为什么当writer（io.Writer的实现）尝试调用Write()函数时，会显示这个错误信息：
this.writer.Write未定义（*io.Writer类型没有Write字段或方法）
英文:
package main
import "io"
type MyClass struct{
writer *io.Writer
}
func (this *MyClass) WriteIt() {
this.writer.Write([]byte("Hello World!"))
}
Why is it that when writer, which is an implementation of io.Writer, tries to call the Write() function, displays me this error
> this.writer.Write undefined (type *io.Writer has no field or method
> Write)
答案1
得分: 5
如makhov所说，这是因为在MyClass的结构定义中，writer是一个指向实现了Writer接口的对象的指针，而不是指向实现了writer接口本身的对象。因此，你的代码应该是：
package main
import "io"
type MyClass struct{
writer io.Writer
}
func (this *MyClass) WriteIt() {
this.writer.Write([]byte("Hello World!"))
}
或者
package main
import "io"
type MyClass struct{
writer *io.Writer
}
func (this *MyClass) WriteIt() {
(*(this.writer)).Write([]byte("Hello World!"))
}
通常情况下，第一种选项更合理（也更符合惯用法）。
英文:
As makhov said, it is because writer in your struct definition of MyClass is a pointer to something which implements the Writer interface, not something which implements the writer interface itself. As such, your code should either be:
package main
import "io"
type MyClass struct{
writer io.Writer
}
func (this *MyClass) WriteIt() {
this.writer.Write([]byte("Hello World!"))
}
or
package main
import "io"
type MyClass struct{
writer *io.Writer
}
func (this *MyClass) WriteIt() {
(*(this.writer)).Write([]byte("Hello World!"))
}
Typically it would make sense (and be more idiomatic) to do the first option.
答案2
得分: 2
使用 writer io.Writer 而不是 *writer io.Writer。
英文:
Use writer io.Writer without *
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论