accessing struct from one class to another

问题:

Is it possible to access a struct from another class?

ex:

class A{
    struct structOfClassA {
        func returnLetterA () -> String{
            return "a"
        }
    }
}

class B{
    let classA = A()

    init(){
        classA.structOfClassA.returnLetterA // this is what I want to achieve
    }
}

how can I access the the struct from Class A() in Class B()?

is there a workaround with this?

Thank you!

回答1:

The structure in class A defines a type (that can be used within the scope of class A), but you need an instance of it to be able to call the member functions of the structure. E.g.:

class A {
    struct StructOfClassA {
        func returnLetterA() -> String{
            return "a"
        }
    }

    var structOfClassA = StructOfClassA() 
        /* Instance of 'StructOfClassA' structure type */
}

class B {
    let classA = A()

    init() {
        let myLetter = classA.structOfClassA.returnLetterA()
        print(myLetter)
    }
}

var myB = B() // prints "a"

---

Alternatively, you can let B be a subclass of A, which gives you access to the type StructOfClassA from the superclass, in which case you could create an instance of StructOfClassA and access its method returnLetterA():

class A {
    class StructOfClassA {
        func returnLetterA() -> String{
            return "a"
        }
    }
}

class B : A {
    let classA = A()

    override init() {
        let myLetter = StructOfClassA().returnLetterA()
        print(myLetter)
    }
}

var myB = B() // prints "a"

回答2:

You have just declared the struct A in class A but you also have to create an instance from struct A.

class A{
    struct SomeStruct {
        func returnLetterA () -> String{
            return "a"
        }
    }
    let A = SomeStruct()
}

class B{
    let classA = A()

    init(){
        let letter = classA.A.returnLetterA() // this is what I want to achive
    }
}