致命错误 索引超出范围

Question

我不明白哪里出错了。请帮我解决这个问题。

这是我的代码：

import SpriteKit

class EncounterManager {
    let encounterNames: [String] = ["EncounterName1",
                                    "EncountersName2",
                                    "EncountersName3"]
    var encounters: [SKNode] = []

    var currentEncounterIndex:Int?

    var previousEncounterIndex:Int?


    init() {
        for encounterFileName in encounterNames {
            let encounter = SKNode()
            if let encounterScene = SKScene(fileNamed: encounterFileName) {
                for placeholder in encounterScene.children {

                    if let node = placeholder as? SKNode {

                        switch node.name! {
                        case "N" :
                            let n = N()
                            n.spawn(encounter, position: node.position)

                        case "NN":
                            let nn = NN()
                            nn.spawn(encounter, position: node.position)

                        case "NNN":
                            let nnn  = NNN()
                            nnn.spawn(encounter, position: node.position)

                        case "GGG":
                            let ggg = GGG()
                            ggg.spawn(encounter, position: node.position)

                        case "GG":
                            let gg = GG()
                            gg.spawn(encounter, position: node.position)

                        case "G":
                            let g = G()
                            g.spawn(encounter, position: node.position)

                        case "F":
                            let f = F()
                            ff.spawn(encounter, position: node.position)

                        default:
                            print("Name error: \(node.name)")
                    }
                }
            }
        }
    }
}

    func addToWorld(world:SKNode) {

        for index in (encounters.count).stride(through: 0, by: -1) {

            encounters[index].position = CGPoint(x: -2000, y: index * 1000)
            world.addChild(encounters[index])

       }

   }

}

这是来自控制台的错误：

fatal error: Index out of range

这是错误所在的行：

encounters[index].position = CGPoint(x: -2000, y: index * 1000)

这是行错误：

EXC_BAD_INSTRUCTION(code=EXC_I386_INVOP, subcode=0x0)

我试图在互联网上找到有关此问题的一些信息，但找不到。

Answer 1

改变这一行：

for index in (encounters.count).stride(through: 0, by: -1)

到这里：

for index in (encounters.count.predecessor()).stride(through: 0, by: -1)

您收到错误是因为使用第一个版本，步幅从 encounters.count 开始，它位于最后一个有效索引的后面。