模式匹配如果不爲零

Question

# Let's say I've got the following typealias 
public typealias DateRange = (from: NSDate?, to: NSDate?) 

# And use it here 
var selectedDateRange: DateRange = (nil, nil) 

然後我可以使用模式匹配來獲取值並使用模式匹配將其解包嗎？

# I can check vs. `nil` like so: 

if case (nil, nil) = segmentControl.selectedCustomDateRange { 
    print("Damn, nil!") 
} 

# And I want something shorter than 
if let from = segmentControl.selectedDateRange.from, 
    let to = segmentControl.selectedDateRange.to 
{ 
    model.setPeriod(from, to: to) 
} 

有什麼建議嗎？

Answer 1

可以使用if與模式匹配和可選的模式 x?：

if case let (from?, to?) = selectedDateRange { 
    model.setPeriod(from, to: to) 
} 

Answer 2

以上，但不同的類似......

guard case let (from?, to?) = selectedDateRange else { 
    print("Damn, at least one nil!") 
    return 
} 
model.setPeriod(from, to: to)}