ios - Swift iOS - 按属性比较 1 个数组中的元素

Question

我有一个对象数组，我想根据属性比较这些对象，看看属性是否完全相同。现在我遍历所有对象，将属性的所有值放在一个单独的数组中，然后使用 filterArr.allSatisfy { $0 == filterArr.last } 来确定属性是否相同或不。

此方法有效，但我知道必须有比我正在做的更优雅的方法。

我实际上一直在寻找这个问题的答案，但我遇到的每一件事都是比较 2 个不同数组而不是 1 个数组的元素。

class IceCream {
    var flavor: String?
    var price: Double?
}

let iceCream1 = IceCream()
iceCream1.flavor = "vanilla"
iceCream1.price = 1.5

let iceCream2 = IceCream()
iceCream2.flavor = "chocolate"
iceCream2.price = 2.0

let iceCream3 = IceCream()
iceCream3.flavor = "vanilla"
iceCream3.price = 1.5

let iceCream4 = IceCream()
iceCream4.flavor = "strawberry"
iceCream4.price = 2.5

let iceCreams = [iceCream1, iceCream2, iceCream3, iceCream4]

var filterArr = [String]()

for iceCream in iceCreams {
    filterArr.append(iceCream.flavor ?? "")
}

let areItemsEqual = filterArr.allSatisfy { $0 == filterArr.last }

print(areItemsEqual) // prints false

Answer 1

您可以避免使用结构在单独的行上初始化然后分配属性。

struct IceCream {
    let flavor: String?
    let price: Double?
}

let iceCreams: [IceCream] = [
    IceCream(flavor: "vanilla", price: 1.5),
    IceCream(flavor: "chocolate", price: 2.0),
    IceCream(flavor: "vanilla", price: 1.5),
    IceCream(flavor: "strawberry", price: 2.5)
]

使用 @Alexander 提供的通用糖和 @matt ，我们有一个漂亮的扩展。

extension Collection {
    func allEqual<T: Equatable>(by key: KeyPath<Element, T>) -> Bool {
        return allSatisfy { first?[keyPath:key] == $0[keyPath:key] }
    }
}

print(iceCreams.allEqual(by: \.flavor))

---

或者，您可以指定一个 IceCream 的口味相同。

extension IceCream: Equatable {
    static func == (lhs: IceCream, rhs: IceCream) -> Bool {
        return lhs.flavor == rhs.flavor
    }
}

extension Collection where Element: Equatable {
    func allEqual() -> Bool {
        return allSatisfy { first == $0 }
    }
}

print(iceCreams.allEqual())