如何读取多个json文件

Question

I am trying to read json data from multiple json files. I am not sure how I read each files and concatenate all results

There json files name are test1.json, test2.json test3.json..etc with the same data structure but I am having an issue read then all and my code seems to only show the last one. I have concatenated a string based on the file name but seems to not working for me.

type Book struct {
    Id    string `json: "id"`
    Title string `json: "title"`
}

func main() {
    fileIndex := 2 // three json files. All named test1.json, test2.json and test3.json

    var master []Book

    for i := 0; i <= fileIndex; i++ {
        fileName := fmt.Sprintf("%s%d%s", "test", fileIndex, ".json")

        // Open jsonFile
        jsonFile, err := os.Open(fileName)

        defer jsonFile.Close()

        byteValue, _ := ioutil.ReadAll(jsonFile)
        fmt.Println(byteValue)
        var book []Book

        json.Unmarshal(byteValue, &book)
        fmt.Println(book) // all print shows the test3.json result 
    }
}

I need to be able to read all three json files and hoping to concatenate all results. Can anyone help me? Thank you!

Answer 1

You are using fileIndex while generating the filename instead of using i in the for loop. The code after the changes would be :

type Book struct {
    Id    string `json: "id"`
    Title string `json: "title"`
}

func main() {
    fileIndex := 2 // three json files. All named test1.json, test2.json and test3.json

    var master []Book

    for i := 0; i <= fileIndex; i++ {
        fileName := fmt.Sprintf("%s%d%s", "test", i, ".json")

        // Open jsonFile
        jsonFile, err := os.Open(fileName)

        defer jsonFile.Close()

        byteValue, _ := ioutil.ReadAll(jsonFile)
        fmt.Println(byteValue)
        var book []Book

        json.Unmarshal(byteValue, &book)
        fmt.Println(book)
    }
}

Also, you can do something like master = append(master, book) inside the for loop to finally get all JSON content in master