golang，如何满足同一包中许多文件的接口？

Question

I have this logic of my app:

myapp/
     |- tables/
              |-table1.go
              |-table2.go
              |-table3.go
      - main.go

In main.go I have simple interface:

type DBInterface interface {
    DataParse(string) string
}

Now, table1, table2, tableN are name of tables in DB. I need to perform specific action on specific table. Hence, in table1.go I have simple function which returns parsed data for table1.go, some for the rest.

Now, problem is that I have in main.go function:

func ParseDataFromManyTables(dbs DBInterface) {
    // some actions on tables like: dbs.DataParse("tablename")
    // and these DataParse() are declared in tables/table*.go
}

What I wanted to do is to use function which satisfies interface from each tables/table*.go file (DataParse()). But the problem is - this function cannot be redeclared in same package (tables here), what I can do better here? I know, that I may create new packages(directories) but I does not seem to be correct approach here....

Answer 1

You cannot satisfy an interface with a function. Only types with methods can satisfy an interface.

To satisfy an interface you need to declare a type and then implement a set of methods on that type that match the method signatures of the interface's method set.

In you case you can declare a type in each of your files and for each of those types implement a method that has the same signature as DBInterface's ParseData:

table1.go

package tables

type Table1 struct{}

func (t Table1) DataParse(s string) string {
    // ...
    return "..."
}

table2.go

package tables

type Table2 struct{}

func (t Table2) DataParse(s string) string {
    // ...
    return "..."
}

Given this example you can now pass a value of type Table1 or Table2 to ParseDataFromManyTables.