iOS16.3下Swift日期区间判断方法失效问题排查

问题场景 #

在iOS16.3、Xcode14.2、Swift5.7.2环境中，调用日期区间判断方法时，设置date = Date()且maximumDate = Date()，预期返回true但实际返回false；仅当设置maximumDate = Date().addingTimeInterval(1)时，方法才正常工作。

相关代码 #

public class THManager : ObservableObject {
    
    @Published public var minimumDate: Date = Date()
    @Published public var maximumDate: Date = Date()

    public func isBetweenMinAndMaxDates(date: Date) -> Bool {
        print(min(minimumDate, maximumDate))
        print(max(minimumDate, maximumDate))
        print(min(minimumDate, maximumDate)...max(minimumDate, maximumDate))
        print(date)
        print((min(minimumDate, maximumDate)...max(minimumDate, maximumDate)).contains(date))
        
        return (min(minimumDate, maximumDate)...max(minimumDate, maximumDate)).contains(date)
    }
}

打印结果 #

2022-02-08 19:45:51 +0000
2023-02-03 19:45:51 +0000
2022-02-08 19:45:51 +0000...2023-02-03 19:45:51 +0000
2023-02-03 19:45:51 +0000
false

原因 #

问题核心在于Date的高精度特性和闭区间的判断逻辑：

1. Date类型精度达到纳秒级，你创建的minimumDate、maximumDate和传入的date虽然打印显示时间相同，但实际创建有先后顺序，纳秒级数值存在微小差异。
2. 当maximumDate的实际纳秒值略小于传入的date时，闭区间...的contains方法会判定date超出范围，返回false；给maximumDate加1秒后，其数值必然大于date，判断自然正常。

解决方案 #

方案一：统一精度后比较 #

将所有日期转换为秒级时间戳，消除纳秒差异：

public func isBetweenMinAndMaxDates(date: Date) -> Bool {
    let minTimestamp = min(minimumDate.timeIntervalSince1970, maximumDate.timeIntervalSince1970)
    let maxTimestamp = max(minimumDate.timeIntervalSince1970, maximumDate.timeIntervalSince1970)
    let dateTimestamp = date.timeIntervalSince1970
    return dateTimestamp >= minTimestamp && dateTimestamp <= maxTimestamp
}

方案二：直接使用上下限比较 #

替代区间判断逻辑，直接进行日期大小比较，更直观且避免精度问题：

public func isBetweenMinAndMaxDates(date: Date) -> Bool {
    let lowerBound = min(minimumDate, maximumDate)
    let upperBound = max(minimumDate, maximumDate)
    return date >= lowerBound && date <= upperBound
}

内容的提问来源于stack exchange，提问作者iKK