Swift 中当月的第一天和最后一天

在 Swift 中，我们可以很方便地获取当前月份的第一天和最后一天的日期。这对于很多日常应用场景非常有用，比如统计当月的数据、生成当月的日历等等。下面我们就来看一下如何使用 Swift 来获取当月的第一天和最后一天。

swift
import Foundation
let currentDate = Date()
let calendar = Calendar.current
let components = calendar.dateComponents([.year, .month], from: currentDate)
let startOfMonth = calendar.date(from: components)!
let endOfMonth = calendar.date(byAdding: DateComponents(month: 1, day: -1), to: startOfMonth)!

swift
let data = [
    (date: startOfMonth, value: 10),
    (date: startOfMonth, value: 20),
    (date: endOfMonth, value: 30),
    // ...
]
let sumOfMonth = data.filter { calendar.isDate($0.date, equalTo: startOfMonth, toGranularity: .month) }
                    .reduce(0) { $0 + $1.value }
print("当月的数据总和为：\(sumOfMonth)")

swift
let numberOfDaysInMonth = calendar.range(of: .day, in: .month, for: startOfMonth)!.count
for day in 1...numberOfDaysInMonth {
    let dateComponents = DateComponents(year: components.year, month: components.month, day: day)
    let date = calendar.date(from: dateComponents)!
    
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd"
    let dateString = dateFormatter.string(from: date)
    
    print(dateString)
}