替换多维数组中的值

Question

我有一个由包含多个数组的结构组成的数组，当尝试替换子数组中的值时遇到错误：

致命错误：索引超出范围

  struct Main {
  var city: String
  var pop: Int
  var color: String
}

class Home {
    
var mainArray = [[Main]]()

func update() {
    let data = Main(city: "SF", pop: 2, color: "orange")
    mainArray.append(data)
    
    for var subArray in mainArray {
        for var i in subArray {
          var newCity = "SB"
          
           i.city = newCity
           subArray[0].city = i.city
       }

    }
  }
}

Answer 1

您的代码将永远无法工作，因为由于值语义，您将修改数组和子数组的副本。

你必须直接修改原始数组，像这样

struct Main {
  var city: String
  var pop: Int
  var color: String
}

var mainArray = [[Main(city: "SF", pop: 1, color: "blue")], [Main(city: "NYC", pop: 2, color: "white")]]

for (index,  subArray) in mainArray.enumerated() {
    for (subIndex, _) in subArray.enumerated() {
        let newCity = "SB"
        mainArray[index][subIndex].city = newCity
    }
    
}