How to achieve chain calls with Struct in Swift-CodePudding

How to achieve a similar chain style with struct, do comment if it's a duplicate.

class Employee {
    
    var name: String?
    var designation: String?
    
    func name(_ name: String) -> Employee {
        self.name = name
        return self
    }
    
    func designation(_ designation: String) -> Employee {
        self.designation = designation
        return self
    }
}

/// Usage
let emp = Employee()
    .name("Speedy")
    .designation("iOS Enigineer")

print(emp.designation)

CodePudding user response：

You should call the initialiser of the struct and pass it the given value:

struct Employee {
    
    var name: String?
    var designation: String?
    
    func name(_ name: String) -> Employee {
        .init(name: name, designation: self.designation)
    }
    
    func designation(_ designation: String) -> Employee {
        .init(name: self.name, designation: designation)
    }
}

If all the methods that you are chaining are boring property setters, you might as well just call the automatically generated initialisers:

// either parameter can be omitted!
Employee(name: "...", designation: "...")

This sort of chaining is only really useful when there are more complicated things going on with your properties. For example, when 2 properties must be set at the same time, or if you require generic parameters when setting those properties. For a good example of this, see how SwiftUI does this.