我熟悉Swift中的switch语句，但想知道如何用开关替换这段代码：
if someVar < 0 {
// do something
} else if someVar == 0 {
// do something else
} else if someVar > 0 {
// etc
}
这里有一种方法。假设someVar是Int或其他Comparable，您可以选择将操作数分配给一个新变量。这使您可以使用where关键字来定义范围：
原文链接：https://www.f2er.com/swift/321252.htmlvar someVar = 3
switch someVar {
case let x where x < 0:
print("x is \(x)")
case let x where x == 0:
print("x is \(x)")
case let x where x > 0:
print("x is \(x)")
default:
print("this is impossible")
}
这可以简化一点：
switch someVar {
case _ where someVar < 0:
print("someVar is \(someVar)")
case 0:
print("someVar is 0")
case _ where someVar > 0:
print("someVar is \(someVar)")
default:
print("this is impossible")
}
您还可以避免where关键字完全使用范围匹配：
switch someVar {
case Int.min..<0:
print("someVar is \(someVar)")
case 0:
print("someVar is 0")
default:
print("someVar is \(someVar)")
}
