swift - 更改数组中的属性值

Question

当我尝试为数组属性分配新值时，出现错误:无法分配给属性:“color”是“let”常量

struct car {
    let model: String
    let color: String
}

var myCars :[car] = [
    car(name:"model X", color: "black"),
    car(name:"model Y", color: "blue"),
    car(name:"roadster", color: "red"),
    car(name:"model S", color: "black"),
    car(name:"model 3", color: "black")
]

let colorFilter = dataSource.items.index(where: {$0.color == "black"})
myCars[colorFilter].color = "grey"

将所有颜色属性设置为“黑色”的项目替换为“灰色”

Answer 1

自 color是 constant (let) property ，即一次initialised你不能改变它的值。如果您想修改 color 的值，让它var而不是let

struct car {
    let model: String
    var color: String
}

更新color全部cars来自black to grey ，使用 map(_:) myCars数组。

myCars = myCars.map {
    var newCar = $0
    if newCar.color == "black" {
        newCar.color = "grey"
    }
    return newCar
}

输出:

print(myCars)

// [car(model: "model X", color: "grey"), car(model: "model Y", color: "blue"), car(model: "roadster", color: "red"), car(model: "model S", color: "grey"), car(model: "model 3", color: "grey")]