OptionalAssignment.swift

OptionalAssignment.swift

// Optional Assignment

infix operator =? { associativity right precedence 90 }

/// Given a variable and an optional value it unwraps the optional value
/// and if it is non-nil it assigns the value to the variable. If the value
/// is nil it does nothing.
public func =? <T>(inout variable: T, optionalValue: T?) {
    if let value = optionalValue {
        variable = value
    }
}

func before() -> String {
    var variable: String = "InitialValue"
    
    let optionalValue1: String? = nil
    let optionalValue2: String? = "NewValue"
    
    if let value1 = optionalValue1 {
        variable = value1 // "InitialValue"
    }
    
    if let value2 = optionalValue2 {
        variable = value2 // "NewValue"
    }
    
    return variable
}

func after() -> String {
    var variable: String = "InitialValue"
    
    let optionalValue1: String? = nil
    let optionalValue2: String? = "NewValue"
    
    variable =? optionalValue1 // "InitialValue"
    variable =? optionalValue2 // "NewValue"
    
    return variable
}