Instead of asserting the type every time in a switch statement, assign the result of type assertion to a variable and use it.

A type assertion provides access to an interface's underlying concrete value. The following statement asserts that the interface value i holds the concrete type T assigns the underlying T value to the variable t. The statement will trigger panic if i does not hold a T.

t := i.(T)

Hence, the recommendation of using the result of type assertion is idiomatic and straightforward. Also, it saves from the following bad practice:

switch x.(type) {
case int:
    // Triggers a panic as "x" doesn't hold
    // concrete type "string" but "int"
    fmt.Println(x.(string))
}

Bad practice

switch x.(type) {
case int:
    fmt.Println(x.(int))
}

Recommended

switch x := x.(type) {
case int:
    fmt.Println(x)
}

beego / beego

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