Make a ViewModifier that does the numeric filtering

Author: amayers

Sources/NumericText/NumberFormatter+Decimal.swift

@@ -0,0 +1,7 @@
+import Foundation
+
+var decimalNumberFormatter: NumberFormatter = {
+    let formatter = NumberFormatter()
+    formatter.numberStyle = .decimal
+    return formatter
+}()

Sources/NumericText/NumericTextField.swift

@@ -7,7 +7,6 @@ public struct NumericTextField: View {
     @Binding private var number: NSNumber?
     @State private var string: String
     private let isDecimalAllowed: Bool
-    private let formatter: NumberFormatter = NumberFormatter()
 
     private let title: LocalizedStringKey
     private let onEditingChanged: (Bool) -> Void
@@ -24,9 +23,8 @@ public struct NumericTextField: View {
     ///     The closure receives a Boolean indicating whether the text field is currently being edited.
     ///   - onCommit: An action to perform when the user performs an action (for example, when the user hits the return key) while the text field has focus.
     public init(_ titleKey: LocalizedStringKey, number: Binding<NSNumber?>, isDecimalAllowed: Bool, onEditingChanged: @escaping (Bool) -> Void = { _ in }, onCommit: @escaping () -> Void = {}) {
-        formatter.numberStyle = .decimal
         _number = number
-        if let number = number.wrappedValue, let string = formatter.string(from: number) {
+        if let number = number.wrappedValue, let string = decimalNumberFormatter.string(from: number) {
         _string = State(initialValue: string)
         } else {
             _string = State(initialValue: "")
@@ -38,18 +36,10 @@ public struct NumericTextField: View {
     }
 
     public var body: some View {
-        return TextField(title, text: $string, onEditingChanged: onEditingChanged, onCommit: onCommit)
-            .onChange(of: string, perform: numberChanged(newValue:))
+        TextField(title, text: $string, onEditingChanged: onEditingChanged, onCommit: onCommit)
+            .numericText(text: $string, number: $number, isDecimalAllowed: isDecimalAllowed)
             .modifier(KeyboardModifier(isDecimalAllowed: isDecimalAllowed))
     }
-
-    private func numberChanged(newValue: String) {
-        let numeric = newValue.numericValue(allowDecimalSeparator: isDecimalAllowed)
-        if newValue != numeric {
-            string = numeric
-        }
-        number = formatter.number(from: string)
-    }
 }
 
 private struct KeyboardModifier: ViewModifier {

Sources/NumericText/NumericTextModifier.swift

@@ -0,0 +1,44 @@
+import SwiftUI
+
+/// A modifier that observes any changes to a string, and updates that string to remove any non-numeric characters.
+/// It also will convert that string to a `NSNumber` for easy use.
+public struct NumericTextModifier: ViewModifier {
+    /// Should the user be allowed to enter a decimal number, or an integer
+    public let isDecimalAllowed: Bool
+    /// The string that the text field is bound to
+    @Binding public var text: String
+    /// A number that will be updated when the `text` is updated.
+    @Binding public var number: NSNumber?
+
+    /// A modifier that observes any changes to a string, and updates that string to remove any non-numeric characters.
+    /// It also will convert that string to a `NSNumber` for easy use.
+    ///
+    /// - Parameters:
+    ///   - text: The string that this should observe and filter
+    ///   - number: A number that should be updated whenever the `text` is updated
+    ///   - isDecimalAllowed: Should the user be allowed to enter a decimal number, or an integer
+    public init(text: Binding<String>, number: Binding<NSNumber?>, isDecimalAllowed: Bool) {
+        _text = text
+        _number = number
+        self.isDecimalAllowed = isDecimalAllowed
+    }
+
+    public func body(content: Content) -> some View {
+        content
+            .onChange(of: text) { newValue in
+                let numeric = newValue.numericValue(allowDecimalSeparator: isDecimalAllowed)
+                if newValue != numeric {
+                    text = numeric
+                }
+                number = decimalNumberFormatter.number(from: numeric)
+            }
+    }
+}
+
+public extension View {
+    /// A modifier that observes any changes to a string, and updates that string to remove any non-numeric characters.
+    /// It also will convert that string to a `NSNumber` for easy use.
+    func numericText(text: Binding<String>, number: Binding<NSNumber?>, isDecimalAllowed: Bool) -> some View {
+        modifier(NumericTextModifier(text: text, number: number, isDecimalAllowed: isDecimalAllowed))
+    }
+}