我想使一些与分配不兼容的Integer类型,如下所示。
typealias Fatty = Int
typealias Skinny = Int
var a : Fatty = 6
var b: Skinny = 4
a = b // This should throw a compile time error saying the types are incompatible
a = Fatty(b) // this should work
有什么办法可以迅速地做到这一点(无需创建类/结构)?过去能够以Pascal做到这一点。
答案 0 :(得分:5)
是的,您可以定义自己的整数类型,但这并不容易:
public struct Fatty: ExpressibleByIntegerLiteral, Hashable {
public typealias IntegerLiteralType = Int
let value: Int
public init(_ value: Int) {
self.value = value
}
public init(_ skinny: Skinny) {
self.value = skinny.value
}
public init(integerLiteral value: Int) {
self.value = value
}
}
public struct Skinny: ExpressibleByIntegerLiteral, Hashable {
public typealias IntegerLiteralType = Int
let value: Int
public init(_ value: Int) {
self.value = value
}
public init(_ fatty: Fatty) {
self.value = fatty.value
}
public init(integerLiteral value: Int) {
self.value = value
}
}
如果您希望类型表现得像实整数一样,则可以使它们符合BinaryInteger
(或其他整数协议)。
可以使用某种协议进行概括:
public protocol CustomInt: ExpressibleByIntegerLiteral, Hashable, Comparable {
associatedtype ValueType = _ExpressibleByBuiltinIntegerLiteral
var value: ValueType { get set }
init(value: ValueType)
}
extension CustomInt {
public init(integerLiteral value: ValueType) {
self.init(value: value)
}
public init<T: CustomInt>(_ customInt: T) where Self.ValueType == T.ValueType {
self.init(value: customInt.value)
}
}
extension CustomInt where ValueType: Comparable {
public static func < (lhs: Self, rhs: Self) -> Bool {
return lhs.value < rhs.value
}
}
public struct Fatty: CustomInt {
public var value: Int
public init(value: Int) {
self.value = value
}
}
public struct Skinny: CustomInt {
public var value: Int
public init(value: Int) {
self.value = value
}
}