How to use generics with custom types?

php editor Baicao introduces you how to use generics and custom types together. Generics are a technique commonly used in programming to make code more flexible and reusable. Custom types are data types defined by developers themselves based on business needs. When we need to use generics in a custom type, we can do so through generic classes or generic interfaces. By rationally using generics and custom types, we can better improve the maintainability and scalability of the code. In the following articles, we will detail the specific methods and considerations for using generics with custom types.

Question content

I'm really confused about how the rules of generics work. I just want a function to accept multiple custom types and have different logic for each type.

type myObjOne struct {
    myfield        string
}

type myObjTwo struct {
    myObjTwo
    myOtherField   string
}

type Generic interface {
    myObjOne | myObjTwo
}

func derp[T Generic](c T) {
    switch any(c).(type) {
    case myObjOne:
        // I can't access the fields of my types like this
        c.myfield = "sdfsfsdfdsf"
    case myObjTwo:
        c.myOtherField = "sdfsfsdfdsf"
    }
    return
}

Why c.myfield throws c.myfield undefined (type T has no field or method myfield) compilerMissingFieldOrMethod?

Solution

c is the type T, not the result of a type assertion. Fixed by assigning the result of the type assertion to a variable.

func derp[T Generic](c T) {
    switch c := any(c).(type) {
    case myObjOne:
        // I can't access the fields of my types like this
        c.myfield = "sdfsfsdfdsf"
    case myObjTwo:
        c.myOtherField = "sdfsfsdfdsf"
    }
    return
}

This code declares a second variable c in the type switch. The type of c depends on the branch of the switch.

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