英文:
After renaming a type, I cannot access some of its methods
问题
为了避免在项目的不同文件中出现多个依赖项，并且由于我可能会更改数据的呈现方式，我决定为draw2d包创建一个“接口”（不是指golang中的接口，而是指架构上的接口）。
由于我不需要其他内容，我只是重命名了其中一个类型：
type CanvasContext draw2dimg.GraphicContext
在我的一个模块中，我有以下代码（path是一个CanvasContext变量）：
// initialization and some code omitted for clarity
path.SetFillColor(color.RGBA{0x44, 0xff, 0x44, 0xff})
path.SetStrokeColor(color.RGBA{0x44, 0x44, 0x44, 0xff})
path.SetLineWidth(5)
// some more code here
path.Close()
path.FillStroke()
在所有对path的方法调用中，只有FillStroke方法出现了编译错误：
path.FillStroke undefined (type *drawing.CanvasContext has no field or method FillStroke)
为了避免这种情况，我必须重新定义FillStroke方法，但不需要重新定义其他任何方法：
func (cc *CanvasContext) FillStroke() {
gc := draw2dimg.GraphicContext(*cc)
gc.FillStroke()
}
为什么我只需要重新定义FillStroke方法，而不是其他任何方法呢？
英文:
In order to prevent having multiple dependencies along different files of my project and since I might change how data will be presented, I decided to make an "interface" (not in the golang sense but in an architectural way) to the draw2d package
As I didn't need anything else, I just renamed one of the types:
type CanvasContext draw2dimg.GraphicContext
In one of my modules I had the following code (path is a CanvasContext variable):
// initialization and some code omitted for clarity
path.SetFillColor(color.RGBA{0x44, 0xff, 0x44, 0xff})
path.SetStrokeColor(color.RGBA{0x44, 0x44, 0x44, 0xff})
path.SetLineWidth(5)
// some more code here
path.Close()
path.FillStroke()
Among all those method calls on path, only the FillStroke failed with the compile error:
> path.FillStroke undefined (type *drawing.CanvasContext has no field or
> method FillStroke)
In order to prevent it I have to redefine the FillStroke, but not any other method, with:
func (cc *CanvasContext) FillStroke() {
gc := draw2dimg.GraphicContext(*cc)
gc.FillStroke()
}
Why do I have to redefine only that one and not any of the other calls?
答案1
得分: 3
你应该使用结构体嵌入（struct embedding）而不是类型定义（type define）。请查看结构体“embedding”文档：
但是为了提升字段的方法并满足io接口的要求，我们还需要提供转发方法，例如：
func (rw *ReadWriter) Read(p []byte) (n int, err error) {
return rw.reader.Read(p)
}
通过直接嵌入结构体，我们可以避免这种繁琐的操作。
英文:
you should use struct embedding rather than type define. check the struct 'embedding' document:
> but then to promote the methods of the fields and to satisfy the io
> interfaces, we would also need to provide forwarding methods, like
> this:
>
>
> func (rw *ReadWriter) Read(p []byte) (n int, err error) {
> return rw.reader.Read(p) }
>
> By embedding the structs directly, we avoid this bookkeeping.
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