Add support for variables in text style.

Cloudinary/Classes/Core/Features/Helpers/CLDExpression.swift

@@ -286,15 +286,16 @@ import Foundation
     // MARK: - provide content
     public func asString() -> String {
 
-        guard !currentKey.isEmpty && !currentValue.isEmpty else {
-
-            return String()
-        }
+        guard !currentKey.isEmpty else { return String() }
 
-        let key   = replaceAllExpressionKeys(in: currentKey)
-        let value = removeExtraDashes(from: replaceAllUnencodeChars(in: currentValue))
+        let key = replaceAllExpressionKeys(in: currentKey)
 
-        return "\(key)_\(value)"
+        if currentValue.isEmpty {
+            return "\(key)"
+        } else {
+            let value = removeExtraDashes(from: replaceAllUnencodeChars(in: currentValue))
+            return "\(key)_\(value)"
+        }
     }
 
     public func asParams() -> [String : String] {

Cloudinary/Classes/Core/Features/Helpers/Layers/CLDTextLayer.swift

@@ -33,6 +33,7 @@ import Foundation
     internal var fontWeight: String?
     internal var textDecoration: String?
     internal var textAlign: String?
+    internal var textStyle: String?
     internal var stroke: String?
     internal var letterSpacing: String?
     internal var lineSpacing: String?
@@ -66,6 +67,32 @@ import Foundation
         return self
     }
 
+    /**
+     Sets a text style identifier.
+     Note: If this is used, all other style attributes are ignored in favor of this identifier
+
+     - parameter text:          A variable string or an explicit style (e.g. "Arial_17_bold_antialias_best").
+
+     - returns:                 The same instance of CLDTextLayer.
+     */
+    open func setTextStyle(textStyle: String) -> CLDTextLayer {
+        self.textStyle = textStyle
+        return self
+    }
+
+    /**
+     Sets a text style identifier using an expression.
+     Note: If this is used, all other style attributes are ignored in favor of this identifier
+
+     - parameter text:          An expression instance referencing the style.
+
+     - returns:                 The same instance of CLDTextLayer.
+     */
+    open func setTextStyle(expression: CLDExpression) -> CLDTextLayer {
+        self.textStyle = expression.asString()
+        return self
+    }
+
     /**
      Set the name of a font family. e.g. `arial`.
 
@@ -333,7 +360,10 @@ import Foundation
 
         let optionalTextParams = getOptionalTextPropertiesArray()
         let mandatoryTextParams = getMandatoryTextPropertiesArray()
-        if optionalTextParams.isEmpty {
+        if let textStyle = textStyle {
+            components.append([textStyle].joined(separator: "_"))
+        }
+        else if optionalTextParams.isEmpty {
             if !mandatoryTextParams.isEmpty {
                 components.append(mandatoryTextParams.joined(separator: "_"))
             }

Example/Tests/GenerateUrlTests/UrlTests.swift

@@ -1052,6 +1052,29 @@ class UrlTests: BaseTestCase {
         XCTAssertEqual(sut?.createUrl().setTransformation(CLDTransformation().setOverlayWithLayer(CLDFetchLayer(url: "https://res.cloudinary.com/demo/image/upload/sample"))).generate("test"),
                        "\(prefix)/image/upload/l_fetch:aHR0cHM6Ly9yZXMuY2xvdWRpbmFyeS5jb20vZGVtby9pbWFnZS91cGxvYWQvc2FtcGxl/test")
     }
+
+    func testTextStyle() {
+        XCTAssertEqual(sut?.createUrl().setTransformation(CLDTransformation().setVariable("$style", string: "!Arial_12!").chain().setOverlayWithLayer(CLDTextLayer().setText(text: "hello-world").setTextStyle(textStyle: "$style"))).generate("test"), "\(prefix)/image/upload/$style_!Arial_12!/l_text:$style:hello-world/test")
+
+        XCTAssertEqual(sut?.createUrl().setTransformation(CLDTransformation().setVariable("$style", string: "!Arial_12!").chain().setOverlayWithLayer(CLDTextLayer().setText(text: "hello-world").setTextStyle(expression: CLDExpression(value: "$style")))).generate("test"), "\(prefix)/image/upload/$style_!Arial_12!/l_text:$style:hello-world/test")
+    }
+
+    func testTextStyleOverpowerOtherTextAttributes() {
+        let layer = CLDTextLayer()
+            .setText(text: "hello_world")
+            .setFontFamily(fontFamily: "Arial")
+            .setFontSize(18)
+            .setFontStyle(.italic)
+            .setFontWeight(.bold)
+            .setLetterSpacing(4)
+            .setTextStyle(textStyle: "$style")
+
+        let transformation = CLDTransformation().setVariable("$style", string: "!Arial_12!").chain().setOverlayWithLayer(layer)
+        let url = sut?.createUrl().setTransformation(transformation).generate("test")
+
+        XCTAssertNotNil(url)
+        XCTAssertFalse(url!.contains("Arial_18_bold_italic_letter_spacing_4"), "$style should overpower other text attributes.")
+    }
 
     func testOverlayErrors() {
         XCTAssertNil(sut?.createUrl().setTransformation(CLDTransformation().setOverlayWithLayer(CLDTextLayer().setText(text: "text").setFontStyle(.italic))).generate("test"))