Swift 3：类和结构可选项

我正在从编码Obj-c过渡到Swift 3很长一段时间。所以我认为我理解可选项的想法，但我对这个问题感到困惑。假设我有一个叫Monster的课。我也有一个叫Town的结构体。Swift 3：类和结构可选项

struct Town { 
    var population: Int = 0 
    var name: String? 
    var hasSherrif: Bool? 
    var hasTheater: Bool? 
    var hasTownhall: Bool? 
    var hasSchool: Bool? 
    var hasGeneralStore: Bool? 
    var numOfHomes: Int = 0 
}

和怪物......

class Monster { 
    var town: Town? 
    var name: String? 

    func moveToTown(_ thisTown: Town) { 
     town = thisTown 
     if let strName = name, let strTownName = town?.name { 
      print("\(strName) moved to \(strTownName)") 
     } else if let strName = name { 
      print("\(strName) move to a town with no name") 
     } else { 
      print("The monster moved to a town. Might help if you give stuff names, just saying.") 
     } 

    } 
}

在moveToTown（_ thisTown：镇），我怎么能检查是否怪物还没有名字，但镇呢？我想改变这一行：

} else if let strName = name {

喜欢的东西

} else if let strName = name && town?.name == nil {

，然后添加其他条件

} else if strName == nil && let strTownName = town?.name { 
}

感谢，如果有一般的任何可能被清理随时批评。

来源

2017-09-05 PruitIgoe

您不能使用town?.name，因为town不是可选的。

而且不需要town = thisTown一行。只需将参数命名为town即可。

我会这样写：

func moveToTown(_ town: Town) { 
    if let name = name { 
     if let townName = town.name { 
      print("\(name) moved to \(townName)") 
     } else { 
      print("\(name) move to a town with no name") 
     } 
    } else { 
     print("The monster moved to a town. Might help if you give stuff names, just saying.") 
    } 
}

来源

2017-09-05 21:13:48 rmaddy

Swift 3：类和结构可选项

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