来自不同文件的golang接口使用方法

Question

I've method which I want to provide some interface to make it more easier to test

This is the function

File A

func readFile(s source) ([]byte, error) {
        p := fs.GetPath()
        file, err := ioutil.ReadFile(p + "/" + s.path + "/" + "rts.yaml")
        if err != nil {
            return yamlFile, fmt.Errorf("erro reading file : %s", err.Error())
        }
        return file, err
    }

Now I add for it struct

type source struct{
    path string
}

And the interface that the readFile is implementing

type fileReader interface {
    readFile(path string) ([]byte, error)
}

And now I need to call this function from another file but Im getting error while doing this

File B

type source struct {
    path string
}


a := source{}

yamlFile, err := readFile(a)

what am I missing here ?

Answer 1

Import the package containing the source struct in File A and then use that struct to initialize the variable after that pass the variable to the readFile function.

File B

import A
a := A.Source{}

Because source struct in File A is different from source struct in File B. And source struct of File A is implementing the interface that's why you need to import the source struct and then pass it into the function.

One this should be noticed that to make any struct or function exportable you should start the struct or fucntion name with upper case letter.

File A

// make struct exportable
type Source struct{
    path string
}

implemented the interface which is different from

File B

type source struct{
    path string
}

which does not implemented the interface.

Edited

File A

package main

import (
    "fmt"
    "io/ioutil"
    "os"
)

type Source struct {
    Path string
}

type fileReader interface {
    readOneFile() ([]byte, error)
}

func(s Source) readOneFile() ([]byte, error) {
    cwd, err := os.Getwd()
    file, err := ioutil.ReadFile(fmt.Sprintf("%s/file.txt", cwd))
    if err != nil {
        return nil, fmt.Errorf("erro reading file : %s", err.Error())
    }
    return file, err
}

File B

package main

import (
    "fmt"
)

func main() {
    s := Source{}
    data, err := s.readOneFile()
    if err != nil {
        fmt.Errorf("Error in reading the file")
    }
    fmt.Println(string(data))
}