有很多方法可以做到这一点。就个人而言,如果可以避免的话,我不喜欢使用字符串。我宁愿处理日期组件。
下面是为 8:00 和 16:30 创建日期的代码,然后比较日期以查看当前日期/时间是否在该范围内。
它比其他人的代码长,但我认为值得学习如何使用日历对日期进行计算:
编辑#3:
这个答案是很久以前的了。我将在下面留下旧答案,但这是当前的解决方案:
@CodenameDuchess 的回答使用了系统函数,date(bySettingHour:minute:second:of:matchingPolicy:repeatedTimePolicy:direction:)
使用该函数,代码可以简化为:
import UIKit
// The function `Calendar.date(bySettingHour:minute:second)` lets you
// create date objects for a given time in the same day of given date
// For example, 8:00 today
let calendar = Calendar.current
let now = Date()
let eight_today = calendar.date(
bySettingHour: 8,
minute: 0,
second: 0,
of: now)!
let four_thirty_today = calendar.date(
bySettingHour: 16,
minute: 30,
second: 0,
of: now)!
// In recent versions of Swift Date objectst are comparable, so you can
// do greater than, less than, or equal to comparisons on dates without
// needing a date extension
if now >= eight_today &&
now <= four_thirty_today
{
print("The time is between 8:00 and 16:30")
}
为了历史的完整性,下面是旧的 (Swift 2) 答案:
此代码使用 Calendar 对象获取当前日期的日/月/年,并添加所需的小时/分钟组件,然后为这些组件生成日期。
import UIKit
//-------------------------------------------------------------
//NSDate extensions.
extension NSDate
{
/**
This adds a new method dateAt to NSDate.
It returns a new date at the specified hours and minutes of the receiver
:param: hours: The hours value
:param: minutes: The new minutes
:returns: a new NSDate with the same year/month/day as the receiver, but with the specified hours/minutes values
*/
func dateAt(#hours: Int, minutes: Int) -> NSDate
{
let calendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
//get the month/day/year componentsfor today's date.
println("Now = \(self)")
let date_components = calendar.components(
NSCalendarUnit.CalendarUnitYear |
NSCalendarUnit.CalendarUnitMonth |
NSCalendarUnit.CalendarUnitDay,
fromDate: self)
//Create an NSDate for 8:00 AM today.
date_components.hour = hours
date_components.minute = minutes
date_components.second = 0
let newDate = calendar.dateFromComponents(date_components)!
return newDate
}
}
//-------------------------------------------------------------
//Tell the system that NSDates can be compared with ==, >, >=, <, and <= operators
extension NSDate: Equatable {}
extension NSDate: Comparable {}
//-------------------------------------------------------------
//Define the global operators for the
//Equatable and Comparable protocols for comparing NSDates
public func ==(lhs: NSDate, rhs: NSDate) -> Bool
{
return lhs.timeIntervalSince1970 == rhs.timeIntervalSince1970
}
public func <(lhs: NSDate, rhs: NSDate) -> Bool
{
return lhs.timeIntervalSince1970 < rhs.timeIntervalSince1970
}
public func >(lhs: NSDate, rhs: NSDate) -> Bool
{
return lhs.timeIntervalSince1970 > rhs.timeIntervalSince1970
}
public func <=(lhs: NSDate, rhs: NSDate) -> Bool
{
return lhs.timeIntervalSince1970 <= rhs.timeIntervalSince1970
}
public func >=(lhs: NSDate, rhs: NSDate) -> Bool
{
return lhs.timeIntervalSince1970 >= rhs.timeIntervalSince1970
}
//-------------------------------------------------------------
let now = NSDate()
let eight_today = now.dateAt(hours: 8, minutes: 0)
let four_thirty_today = now.dateAt(hours:16, minutes: 30)
if now >= eight_today &&
now <= four_thirty_today
{
println("The time is between 8:00 and 16:30")
}
编辑:
这个答案中的代码已经为 Swift 3 改变了很多。
使用原生的Date 对象而不是使用NSDate 更有意义,而Date 对象是Equatable 和Comparable“开箱即用”。
因此,我们可以摆脱 Equatable 和 Comparable 扩展以及 <、> 和 = 运算符的定义。
然后我们需要对dateAt 函数中的语法进行大量调整,以遵循 Swift 3 语法。新的扩展在 Swift 3 中看起来像这样:
Swift 3 版本:
import Foundation
extension Date
{
func dateAt(hours: Int, minutes: Int) -> Date
{
let calendar = NSCalendar(calendarIdentifier: NSCalendar.Identifier.gregorian)!
//get the month/day/year componentsfor today's date.
var date_components = calendar.components(
[NSCalendar.Unit.year,
NSCalendar.Unit.month,
NSCalendar.Unit.day],
from: self)
//Create an NSDate for the specified time today.
date_components.hour = hours
date_components.minute = minutes
date_components.second = 0
let newDate = calendar.date(from: date_components)!
return newDate
}
}
let now = Date()
let eight_today = now.dateAt(hours: 8, minutes: 0)
let four_thirty_today = now.dateAt(hours: 16, minutes: 30)
if now >= eight_today &&
now <= four_thirty_today
{
print("The time is between 8:00 and 16:30")
}