ios - 字符串格式就像循环中的表 swift4

Question

我遇到了这个问题，我在网上寻找的所有可能的解决方案都没有帮助我。有没有办法制作类似字符串格式的表格？

我期望字符串的输出如下:

Category
 ITEM1     QTY     PRICE      TOTAL
 ITEM2     QTY     PRICE      TOTAL

但是我的输出代码是这样的:

Category
 ITEM1         QTY     PRICE      TOTAL
 ITEM2      QTY      PRICE      TOTAL

Category
 ITEM1             QTY       PRICE        TOTAL
 ITEM2       QTY        PRICE      TOTAL

我发现项目字符串长度是它们没有以我的格式正式对齐的成本，但是有没有办法解决这个问题？我是 swift 的新手。

这是我的代码:

for category in self.categoryList {
        sentence += "Category: \(category)\n"
        for items in self.productList {
            if category == items.category {
                grandTotal += Double(items.qty)! * Double(items.price)!
                let total: Double = Double(items.qty)! * Double(items.price)!
                let item = (items.item as NSString).utf8String
                let qty  = (items.qty as NSString).utf8String
                let price = (items.price as NSString).utf8String
                sentence += String(format: "%-10s%20s%15s%15.02f\n", item!, qty!, price!, total)
            }
        }
        sentence += "\n\n"
        grandTotal = 0
    }

    lblData.text = sentence

Answer 1

您可以将字符串填充到定义的长度:

let elements = ["ITEM1", "QTY", "PRICE", "TOTAL"]

// without padding
var sentence = ""
for e in elements {
    if !sentence.isEmpty {
        sentence += " "
    }
    sentence += e
}

print(sentence)
// prints "ITEM1 QTY PRICE TOTAL"

// with padding
sentence = ""
for e in elements {
    sentence += e.padding(toLength: 10, withPad: " ", startingAt: 0)
}

print(sentence)
// prints "ITEM1     QTY       PRICE     TOTAL     "

或者更简短的形式:

// without padding
var sentence = elements.joined(separator: " ")
print(sentence)

// with padding
sentence = elements.map({$0.padding(toLength: 10, withPad: " ", startingAt: 0)}).joined(separator: " ")
print(sentence)