结合UnitMass和UnitLength阵列

Question

我想两个测量阵列组合：

var unitMasses: [UnitMass] { 
    return [.milligrams, .grams, .kilograms, .ounces, .pounds] 
} 

var unitLengths: [UnitLength] { 
    return [.centimeters, .decimeters, .meters] 
} 

成一个：

var units: [AnyObject] { 
    // This works: 
    return [unitMasses].flatMap{$0} 
    // But I've tried the following and this doesn't: 
    //return ([unitMasses as AnyObject] + [unitVolumes as AnyObject]).flatMap{$0} 
} 

我希望能够能访问元素的属性.symbol在units变量：

var symbols: [String] { 
    return units.map({ unit in unit.symbol }) 
} 

谢谢。

Answer 1

从我的角度来看，这种方式非常直截了当。我没有看到任何需要在之前合并数组。

var symbols = unitMasses.map({$0.symbol}) 
symbols += unitLengths.map({$0.symbol}) 

print(symbols) // ["mg", "g", "kg", "oz", "lb", "cm", "dm", "m"] 

Answer 2

接受的答案效果很好。为了完整性，这是我用它的方式：

var units: [Dimension] { 
    return unitMasses.map({ unit in unit }) + unitLengths.map({ unit in unit }) 
} 

var symbols: [String] { 
    return units.map({ unit in unit.symbol }) 
}