specifier / formatter

💾 程式

import SwiftUI
let pi = Double.pi
let str: LocalizedStringKey = "\(pi, specifier: "%.2f")"

⭐️ 重點

When there is a type (not String) which conforms to ExpressibleByStringInterpolation and its associated StringInterpolation has a method .appendInterpolation(_:specifier:), you can use String Interpolation literals like:

"\(pi, specifier: "%.2f")"

📘 手冊

• SwiftUI ⟩

  • ExpressibleByStringInterpolation

  • LocalizedStringKey

    • LocalizedStringKey.StringInterpolation

      • .appendInterpolation(_:specifier:)

  • Text

• String Programming Guide (👴) ⟩

  • Core Foundation ⟩ String Format Specifiers

  • Formatting String Objects

• Foundation ⟩

  • String ⟩

    • String.LocalizationValue.StringInterpolation ⟩

      • .appendInterpolation(_:specifier:)

  • NSString ⟩ String(format:arguments:)

• Swift ⟩ CVarArg (protocol) - 可以被丟進 String(format:) 當 (variadic) arguments 的。

🗣 討論

• String interpolation with a specifier or formatter? ⭐️
• How to invoke method with CVaListPointer parameters in Swift
• Rounding a double value to x number of decimal places in swift
• Precision String Format Specifier In Swift

👥 相關

• applied for String.
• similar to String Interpolation.
• used by .decimalPlaces()method.