如何在Swift協議練習中對齊表格行和列

根據練習，在標題、作者或評分長于主列/s 中的標題后，表格變得不對齊（更正錯誤后：“重復計數應該是非負數”，通過將 - 更改為 以實作恒定填充需要）。我想保持列寬與給定列中最長的字串一樣長，并調整其他單元格中的間距。我試圖在有條件的 printTable 函式中解決它，但是沒有設法比較 columnLabel 和 item，因為它們在不同的回圈中。還試圖在協議中設定新功能來管理對齊。想不通，如果您可以建議。

protocol TabularDataSource {
    var numberOfRows: Int { get }
    var numberOfColumns: Int { get }
    func label(forColumn column: Int) -> String
    func itemFor(row: Int, column: Int) -> String
}

func printTable(_ dataSource: TabularDataSource & CustomStringConvertible) {
    print("Tab. 1: \(dataSource)")

    var headerRow = "|"

    var columnWidths = [Int]()

    for ii in 0 ..< dataSource.numberOfColumns {
        let columnLabel = dataSource.label(forColumn: ii)
        let columnHeader = " \(columnLabel) |"
        headerRow  = columnHeader
        columnWidths.append(columnLabel.count)
    }
    print(headerRow)

for ii in 0 ..< dataSource.numberOfRows {
    
    var out = "|"
   
        for jj in 0 ..< dataSource.numberOfColumns {
            let item = dataSource.itemFor(row: ii, column: jj)
            let paddingNeeded = columnWidths[jj] - item.count
            let padding = repeatElement(" ", count:   paddingNeeded).joined(separator: "")
            out  = " \(padding)\(item) |"
        }
        print(out)
    }
}

struct Book {
    let title: String
    let author: String
    let rating: Int
}

struct BookCollection: TabularDataSource, CustomStringConvertible {
    let name: String
    var books = [Book]()

    var description: String {
        return ("\(name) book collection")
    }

    init(name: String) {
        self.name = name
    }

    mutating func add(_ book: Book) {
        books.append(book)
    }

    var numberOfRows: Int {
        return books.count
    }

    var numberOfColumns: Int {
        return 3
    }

    func label(forColumn column: Int) -> String {
        switch column {
        case 0: return "Title"
        case 1: return "Author"
        case 2: return "Rating"
        default: fatalError("Invalid column!")
        }
    }

    func itemFor(row: Int, column: Int) -> String {
        let book = books[row]
        switch column {
        case 0: return book.title
        case 1: return String(book.author)
        case 2: return String(book.rating)
        default: fatalError("Invalid column!")
        }
    }
}

var bookCollection = BookCollection(name: "Fantasy")
bookCollection.add(Book(title: "Ava", author: "Reno", rating: 7))
bookCollection.add(Book(title: "Vis", author: "Luc", rating: 7))
bookCollection.add(Book(title: "Te", author: "Julo", rating: 9))

printTable(bookCollection)

uj5u.com熱心網友回復：

您可以向資料源添加一個方法來了解該列的最大長度：

protocol TabularDataSource {
    func width(for column: Int) -> Int
}

執行：

func width(for column: Int) -> Int {
    var labels = (0..<numberOfRows).map { itemFor(row: $0, column: column )}
    labels.append(label(forColumn: column))
    let max = labels.max(by: { $0.count < $1.count })?.count ?? 0
    return max   2 //space before/after
}

然后：

func printTable(_ dataSource: TabularDataSource & CustomStringConvertible) {
    var lines = "|"
    for aColumn in 0..<dataSource.numberOfColumns {
        let label = dataSource.label(forColumn: aColumn)
        let totalOfSpaces = dataSource.width(for: aColumn) - label.count
        let spaces = repeatElement(" ", count: totalOfSpaces / 2).joined(separator: "")
        let additionalSpace = totalOfSpaces % 2 == 0 ? "" : " "
        lines  = "\(additionalSpace)\(spaces)\(label)\(spaces)|"
    }
    lines  = "\n"
    for aRow in 0..<dataSource.numberOfRows {
        lines  = "|"
        for aColumn in 0..<dataSource.numberOfColumns {
            let label = dataSource.itemFor(row: aRow, column: aColumn)
            let totalOfSpaces = dataSource.width(for: aColumn) - label.count
            let additionalSpace = totalOfSpaces % 2 == 0 ? "" : " "
            let spaces = repeatElement(" ", count: totalOfSpaces / 2).joined(separator: "")
            lines  = "\(additionalSpace)\(spaces)\(label)\(spaces)|"
        }
        lines  = "\n"
    }
    print(lines)
}

這可以分解為：

func printTable(_ dataSource: TabularDataSource & CustomStringConvertible) {
    func text(text: String, for width: Int) -> String {
        let totalOfSpaces = width - text.count
        let spaces = repeatElement(" ", count: totalOfSpaces / 2).joined(separator: "")
        let additionalSpace = totalOfSpaces % 2 == 0 ? "" : " "
        return "\(additionalSpace)\(spaces)\(text)\(spaces)|"
    }
        lines = "|"
    for aColumn in 0..<dataSource.numberOfColumns {
        lines  = text(text: dataSource.label(forColumn: aColumn), for: dataSource.width(for: aColumn))
    }
    var lines  = "\n"
    for aRow in 0..<dataSource.numberOfRows {
        lines  = "|"
        for aColumn in 0..<dataSource.numberOfColumns {
            lines  = text(text: dataSource.itemFor(row: aRow, column: aColumn), for: dataSource.width(for: aColumn))
        }
        lines  = "\n"
    }
    print(lines)
}

標籤：

上一篇：iPhone上的故事板加載錯誤

下一篇：使用SPM將Firebase包添加到Xcode會導致構建檔案從200個增加到1800個