Swift：具有多个模式的切换大小写无法绑定到变量

这意味着具有多个模式的案例标签无法声明变量。

这是允许的：

let somePoint = (1, 1)switch somePoint {// Case with multiple patterns without bindingcase (0, _),     (_, 0):    println("((somePoint.0), (somePoint.1)) is on an axis")default:    println("((somePoint.0), (somePoint.1)) is not of an axis")}

这也是允许的：

let somePoint = (1, 1)switch somePoint {// Case with single patterns with bindingcase (0, let y):    println("(0, (y)) is on an axis")case (let x, 0):    println("((x), 0) is on an axis")default:    println("((somePoint.0), (somePoint.1)) is not of an axis")}

但是，这是禁止的：

let somePoint = (1, 1)switch somePoint {// Case with multiple patterns that have bindingscase (0, let y),     (let x, 0):    println("((x), (y)) is on an axis")default:    println("((somePoint.0), (somePoint.1)) is not of an axis")}

上面产生一个错误：

error: 'case' labels with multiple patterns cannot declare variables