Swift 3更好的方法来编写这个if语句

Question

我正在比较GKNoise字段中的值,然后根据噪声级别将tile设置为tileMap

这个if语句是通过四舍五入到最接近的十分来比较这些值,有没有更好的方法来编写它？

if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == -1.0 {
    tileMap.setTileGroup(tileGroup4, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == -0.9 {
    tileMap.setTileGroup(tileGroup4, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == -0.8 {
    tileMap.setTileGroup(tileGroup4, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == -0.7 {
    tileMap.setTileGroup(tileGroup4, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == -0.6 {
    tileMap.setTileGroup(tileGroup4, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == -0.5 {
    tileMap.setTileGroup(tileGroup3, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == -0.4 {
    tileMap.setTileGroup(tileGroup3, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == -0.3 {
    tileMap.setTileGroup(tileGroup3, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == -0.2 {
    tileMap.setTileGroup(tileGroup3, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == -0.1 {
    tileMap.setTileGroup(tileGroup3, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == 0.0 {
    tileMap.setTileGroup(tileGroup2, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == 0.1 {
    tileMap.setTileGroup(tileGroup2, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == 0.2 {
    tileMap.setTileGroup(tileGroup2, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == 0.3 {
    tileMap.setTileGroup(tileGroup2, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == 0.4 {
    tileMap.setTileGroup(tileGroup2, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == 0.5 {
    tileMap.setTileGroup(tileGroup1, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == 0.6 {
    tileMap.setTileGroup(tileGroup1, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == 0.7 {
    tileMap.setTileGroup(tileGroup1, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == 0.8 {
    tileMap.setTileGroup(tileGroup1, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == 0.9 {
    tileMap.setTileGroup(tileGroup1, forColumn: columns, row: rows)
}
if round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) == 1.0 {
    tileMap.setTileGroup(tileGroup1, forColumn: columns, row: rows)
}

它似乎有点抽出而且效率不高.

Answer 1

一个相对简单的改进是round在条件之外进行计算,使用变量来存储要使用的标题组的决策,并将链转换为if-then-else.这将让你使用<=和=>代替==:

let rounded = round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows))))
var tileGroup : SKTileGroup = nil
if rounded <= -0.6 {
    tileGroup = titleGroup4
} else if rounded <= -0.1 {
    tileGroup = titleGroup3
} else if rounded <= 0.4 {
    tileGroup = titleGroup2
} else if rounded <= 1.0 {
    tileGroup = titleGroup1
}
tileMap.setTileGroup(tileGroup, forColumn: columns, row: rows)

Answer 2

你可以使用switch和interval matching

switch round(MasterNoise.value(atPosition: vector_float2(Float(columns),Float(rows)))) {
case -1.0...(-0.6):
    tileMap.setTileGroup(tileGroup4, forColumn: columns, row: rows)
case -0.5...(-0.1):
    tileMap.setTileGroup(tileGroup3, forColumn: columns, row: rows)
case 0.0...0.4:
    tileMap.setTileGroup(tileGroup2, forColumn: columns, row: rows)
case 0.5...1.0:
    tileMap.setTileGroup(tileGroup1, forColumn: columns, row: rows)
default:
    break
}