Go中未定义的变量

Question

I'm getting an error: undefined: req during compilation. I understand why I'm getting the error but I'm not sure how to overcome it. This is my code:

switch path {
case "user.save":
    var req SaveRequest
case "user.update": 
    var req UpdateRequest
}

err := c.BindJSON(&req)
if  err != nil {
    c.JSON(http.StatusOK, gin.H{"error_code": "SERVER_ERROR", "message": "Request is not valid JSON"})
    return   
}

c.Set("req", req)

I'm trying to parse JSON requests and then add them to the context. I reaslise that if I define my req variable before the switch statement then this should overcome the problem but I don't know what type to declare it as initially?

Answer 1

Go is lexically scoped using blocks. This means that the declarations of req are only visible within their code block, the case block in this instance.

You need to declare req in the same scope, or an outer scope, from where you want to use it.

var req interface{}
switch path {
case "user.save":
    req = &SaveRequest{}
case "user.update": 
    req = &UpdateRequest{}
}

err := c.BindJSON(req)