如何在Swift3中為Picker索引區域和繪圖圖表添加日期

Question

Swift 3，領域，圖表

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屏幕上有一個DatePicker和BarChart

我想要

1）選擇一個日期2）為我的領域數據庫建立索引3）繪制條形圖

已經有一個領域數據庫

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用於精確索引我將日期分隔為YYYY〜mm

class ChartsDatas: Object {
dynamic var date: Date = Date()

let dateYYYYFormat = DateFormatter()
let dateMMFormat = DateFormatter()
let dateddFormat = DateFormatter()
let datehhFormat = DateFormatter()
let datemmFormat = DateFormatter()
dynamic var dateYYYY: String = "2000"
dynamic var dateMM: String = "01"
dynamic var datedd: String = "01"
dynamic var datehh: String = "00"
dynamic var datemm: String = "00"

dynamic var count: Double = Double(0.0)

func dateLongToShort(orgDate:Date!){
    dateYYYYFormat.dateFormat = "YYYY"
    dateYYYY = dateYYYYFormat.string(from: orgDate)

    dateMMFormat.dateFormat = "MM"
    dateMM = dateMMFormat.string(from: orgDate)

    dateddFormat.dateFormat = "dd"
    datedd = dateddFormat.string(from: orgDate)

    datehhFormat.dateFormat = "hh"
    datehh = datehhFormat.string(from: orgDate)

    datemmFormat.dateFormat = "mm"
    datemm = datemmFormat.string(from: orgDate)
}

繪制（此方法繪制最新的十個數據）

    var dataEntries: [BarChartDataEntry] = []
    let visitorCounts = getVisitorCountsFromDatabase() //read realm DB here

    var xAxisCount = visitorCounts.count 
    if xAxisCount > 10{
        xAxisCount = visitorCounts.count - 10
    }
    for i in xAxisCount..<visitorCounts.count {
        let timeIntervalForDate: TimeInterval = visitorCounts[i].date.timeIntervalSince1970
        let dataEntry = BarChartDataEntry(x: Double(timeIntervalForDate), y: Double(visitorCounts[i].count))
        dataEntries.append(dataEntry)
    }

如何根據我選擇的日期修改以繪制十個數據

謝謝

Answer 1

我不確定getVisitorCountsFromDatabase()發生了什么，但是您可以通過指定日期間隔來過濾帶有謂詞的查詢結果，請參見此處的文檔： https : //realm.io/docs/swift/latest/#filtering