Fix FieldHexadecimal command: missing indicator

Author: scchn

Sources/ZPLBuilder/Commands/FieldHexadecimal.swift

@@ -8,12 +8,23 @@
 import Foundation
 
 public struct FieldHexadecimal: ZPLCommandConvertible {
+    /// Hexadecimal indicator
+    ///
+    /// Values: any character except current format and control prefix (^ and ~ by default)
+    ///
+    /// Default: _ (underscore)
     public var indicator: Character
+    /// Special character's hexadecimal value.
     public var code: UInt8
     public var command: String {
-        String(format: "%02X", code)
+        String(format: "\(indicator)%02X", code)
     }
 
+    /// Field Hexadecimal
+    ///
+    /// - Parameters:
+    ///   - indicator: Hexadecimal indicator. Values: any character except current format and control prefix (^ and ~ by default).
+    ///   - code: Special character's hexadecimal value.
     public init(indicator: Character = "_", code: UInt8) {
         self.indicator = indicator
         self.code = code

Tests/ZPLBuilderTests/ZPLCommandTests.swift

@@ -29,4 +29,12 @@ class ZPLCommandTests: XCTestCase {
         let cmd = BarcodeDefault(moduleWidth: 1, ratio: 2, height: 4)
         XCTAssertEqual(cmd.command, "^BY1,2.0,4")
     }
+    
+    func test_field_hexadecimal() {
+        let cmd1 = FieldHexadecimalIndicator(indicator: "\\")
+        XCTAssertEqual(cmd1.command, "^FH\\")
+        
+        let cmd2 = FieldHexadecimal(indicator: "\\", code: 0x7E)
+        XCTAssertEqual(cmd2.command, "\\7E")
+    }
 }