使用 Guard 捕获除一个之外的所有枚举状态
使用后卫击中障碍物。理想情况下，想要执行一个保护语句来捕获除一个之外的所有枚举状态，因此会类似于：
guard case .notInUse != foundTransition.validToObject.isInSituation else {
fatalError("Transition: The toObject is already in a situation")
}
但似乎不允许这种不匹配的测试。因此，请使用下面的 if 语句：
if case .notInUse = foundTransition.validToObject.isInSituation {} else {
fatalError("Transition: The toObject is already in a situation")
}
它可以工作，但感觉守卫会更整洁。有什么想法吗？
Hitting a block on using a guard. Ideally want to do a guard statement that traps all enum states other than one, so would be something like:
guard case .notInUse != foundTransition.validToObject.isInSituation else {
fatalError("Transition: The toObject is already in a situation")
}
But this non matching test does not seem to be allowed. So instead using the below if statement:
if case .notInUse = foundTransition.validToObject.isInSituation {} else {
fatalError("Transition: The toObject is already in a situation")
}
It works but feels a guard would be neater. Any ideas?
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不可能否定
case语句。您要么需要使用
if语句，要么进行枚举Equatable，在这种情况下，您只需删除 case 关键字即可。或者，您可以使用由
switch或if支持的guard语句。但你永远摆脱不了它们！It is impossible to negate a
casestatement.You either need to use your
ifstatement, or make the enumerationEquatable, in which case you would just drop the case keyword.Alternatively, you can use a
guardstatement that is backed by aswitchorif. But you'll never get rid of them! ????