Golang无法在视图中显示检索到的数据

Question

Hopefully this is my last question to do with pointers ever:

I am calling a repository method to get a slice of gym classes. I am displaying them in a view like this:

    {{ range .}}
            {{.VideoPath}} << Correct
            <br>
            {{.Instructor.Email}} << Blank
            <br>
            {{.ClassType.ClassTypeCode}} << Blank               
    {{end}}   

The instructor and classtype fields are coming up as empty structs, but in the ClassRepository I did some Printlns and the correct data gets printed. Somewhere there is a pointer issue or something. What have I done wrong?

Here is the repository:

package repositories    

type ClassRepository struct {
    Gorp gorp.SqlExecutor
}

func (c ClassRepository) ClassesForLastNDays(days int) []entities.Class {
    var classes []entities.Class
    // Gets the classes - omitted for brevity
    c.populateClassRelationships(classes)
    return classes
}

func (c ClassRepository) populateClassRelationships(classes []entities.Class) {
    for i := range classes {
        class := classes[i]

        // ClassType
        obj, err := c.Gorp.Get(entities.ClassType{}, class.ClassTypeCode)
        if err != nil {
            panic(err)
        }
        class.ClassType = *obj.(*entities.ClassType)
        fmt.Println(class.ClassType) << Returns correct data

        // Instructor and Equipment
        Same for instructor and Equipment


    }

}

UPDATE:

After a whole lot of printlns I can confirm that the issue is here after populateClassRelationships the populated values are all lost.

func (c ClassRepository) ClassesForLastNDays(days int) []entities.Class {
        var classes []entities.Class
        // Gets the classes - omitted for brevity
        c.populateClassRelationships(classes) <<<< In the method,Println has values
        return classes <<<< Values have been lost
    }

Answer 1

I believe the issue is with your function populateClassRelationships where it is not modifying the original data structure as illustrated by the following code which finally outputs:

[1]
[]

Not working

func myFunc(data []int) {
    data = append(data, 1)
    fmt.Println(data)
}

func main() {
    d := []int { }
    myFunc(d)
    fmt.Println(d)
}

With the introduction of the parameters as a pointer the original data can be modified

func myFuncNew(data *[]int) {
        *data = append(*data, 1)
    fmt.Println(*data)
}