Swift的Array的常见扩展

参考：

• https://github.com/lixiang1994/AttributedString
• https://github.com/lixiang1994/AttributedString/blob/master/Sources/Extension/ArrayExtension.swift

前言

项目中使用Swift的Array场景很多，其中数据转换、过滤、分组、去重等相关方法使用很频繁，特记录下

extension Array {
    // 将元素进行分组
    func toGroupedList<E: Equatable>(closure: (Element) -> E?) -> [E: [Element]] {
        return reduce(into: [E: [Element]]()) { (result, e) in
            // 分组的key, 这里支持optional是为了调用时减少判断代码
            if let groupKey = closure(e) {
                // 之前的列表
                let preList = result[groupKey] ?? []
                result[groupKey] = preList + [e]
            }
        }
    }
    
    // 将数据转换为字典
    func toDict<E: Equatable>(closure: (Element) -> E?) -> [E: Element] {
        return reduce(into: [E: Element]()) { (result, e) in
            // 转换为dict的key，这里支持optional是为了调用时减少判断代码
            if let dictKey = closure(e) {
                result[dictKey] = e
            }
        }
    }
    
    // 对内容进行过滤
    func toDeduplicationList<E: Equatable>(closure: (Element) -> E?) -> [Element] {
        return reduce(into: [Element]()) { (result, e) in
            // 元素的唯一性key，这里支持optional是为了调用时减少判断代码
            let uniqueKey = closure(e)
            // 查询之前的列表里是否存在于当前key一样的元素
            let contains = result.contains { closure($0) == uniqueKey }
            // 如果已经存在该元素，不加入，如果不存在该元素，添加该元素
            result = result + (contains ? [] : [e])
        }
    }
    
    // 数组截取
    func subArray(from: Int, size: Int) -> Array<Element> {
        return self.subArray(from: from, to: from+size-1)
    }
    
    func subArray(from: Int) -> Array<Element> {
        return self.subArray(from: from, to: self.count-1)
    }
    
    func subArray(to: Int) -> Array<Element> {
        return self.subArray(from: 0, to: self.count-1)
    }
    
    func subArray(from: Int, to: Int) -> Array<Element> {
        // 可截取的最大值
        let maxTo: Int = self.count - 1
        var fromIndex = from
        if fromIndex < 0 {
            fromIndex = 0
        }
        if fromIndex >= maxTo {
            return []
        }
        var toIndex = to
        if toIndex < 0 {
            toIndex = 0
        }
        if toIndex > maxTo {
            toIndex = maxTo
        }
        if toIndex <= fromIndex {
            return []
        }
        return Array(self[from...toIndex])
    }
}

测试Demo

let list = [1,2,2,3,3,6]
// 去重
let depList = list.toDeduplicationList { $0 }
// 将数字转换为字符串的字符串
let listDict = list.toDict{ "\($0)" }
// 按奇偶数数据进行分组
let groupDict = list.toGroupedList { $0 % 2 }
let subList = list.subArray(from: 2)
let mapList = list.map { $0 + 1 }
let fileterList = list.filter{ $0 > 2}
print(list, depList, listDict, groupDict, subList, mapList, fileterList)