Question

我在swift中使用默认排序算法。但是对于10000（10k）的记录，在ipad上需要花费大约1分钟的时间。

private var fd: [[String:AnyObject]]? = [[String:AnyObject]]()

这是我的降序代码

self.fd = self.fd!.sort ({ (r1, r2) -> Bool in
let t = self.headers![b.tag - 10]
if r1[t.title] is String {
    let dateFormatter = NSDateFormatter()
    dateFormatter.dateFormat = "dd-MMM-yyyy"
    if dateFormatter.dateFromString("\(r1[t.title]!)") != nil {
        let d1 = dateFormatter.dateFromString("\(r1[t.title]!)")
        let d2 = dateFormatter.dateFromString("\(r2[t.title]!)")
        return d1 > d2
    } else {
        // return "\(r1[t.title])".localizedStandardCompare("\(r2[t.title])") == .OrderedDescending
        return "\(r1[t.title])" > "\(r2[t.title])"
    }
} else if r1[t.title] is Int {
    return Int(String(r1[t.title]!)) > Int(String(r2[t.title]!))
} else {
    // return "\(r1[t.title])".localizedStandardCompare("\(r2[t.title])") == .OrderedDescending
    return "\(r1[t.title])" > "\(r2[t.title])"
}})

升序

self.fd = self.fd!.sort ({
(r1, r2) -> Bool in
let t = self.headers![b.tag - 10]
if r1[t.title] is String {
    let dateFormatter = NSDateFormatter()
    dateFormatter.dateFormat = "dd-MMM-yyyy"
    if dateFormatter.dateFromString("\(r1[t.title]!)") != nil {
        let d1 = dateFormatter.dateFromString("\(r1[t.title]!)")
        let d2 = dateFormatter.dateFromString("\(r2[t.title]!)")
        return d1 < d2
    } else {
        //return "\(r1[t.title])".localizedStandardCompare("\(r2[t.title])") == .OrderedAscending
        return "\(r1[t.title])" < "\(r2[t.title])"
    }
} else if r1[t.title] is Int {
    return Int(String(r1[t.title]!)) < Int(String(r2[t.title]!))
} else {
    // return "\(r1[t.title])".localizedStandardCompare("\(r2[t.title])") == .OrderedAscending
    return "\(r1[t.title])" < "\(r2[t.title])"
}})

主要问题是大于10k的数据需要超过60秒。请为我提供解决方案。

Answer 1

您的排序的主要性能问题是您在比较闭包中执行转换。这将调用值格式化过程的指数次数（基于数组的大小）。

更有效的方法是使用.map（）仅执行一次转换，并将sort函数应用于结果。

以下示例基于您的代码使用函数提取排序值，而.map（）仅对数组中的每个元素执行一次此提取：

// only initialize your date formatter once
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "dd-MMM-yyyy"

// Extract the appropriate value and returns it in one of 3 types
// sorting will compare the 3 typed values knowing that only one of the 3
// will actually differ for a given data type
// 
// The element is returned in the tupple in order to rebuild the
// array content after sorting on the 3 values
func getSortValues(_ element:[String:Any], _ id:String) -> ([String:Any], String, Int, TimeInterval)
{
    let value          = element[id]
    var stringOrder    = ""
    var numericOrder   = 0
    var dateOrder      = TimeInterval(0)

    if let stringValue = value as? String,
       let dateValue   = dateFormatter.date(from:stringValue)   
    { 
      dateOrder = dateValue.timeIntervalSinceReferenceDate 
    }
    else if let intValue = value as? Int
    {
      numericOrder     = intValue
    }
    else if value != nil
    {
      stringOrder  = "\(value!)"  
    }
    return (element, stringOrder, numericOrder, dateOrder)
}

let columnId = headers![b.tag - 10]
fd = fd!.map{ getSortValues($0, columnId) } 
        .sorted{ $0.1 < $1.1 || $0.2 < $1.2 || $0.3 < $1.3 }
        .map{ $0.0 }

应该快10到30倍（取决于阵列的大小）。

哪种是在Swift中对大量文本记录进行排序的最快排序技术？

1 个答案: