[Swift4] Fix default value for enums (#652) (#656)

This fixes an issue that makes the swift 4 api client fail to compile when using enums with a default value.
The fix changes the toDefaultValue method to check if the property is of enum type, and then returns a properly formatted value.
Looking into the code, I wonder why toEnumDefaultValue is not being used here, which seems to be the case for the java implementation.

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift4Codegen.java

@@ -510,6 +510,11 @@ public class Swift4Codegen extends DefaultCodegen implements CodegenConfig {
 
     @Override
     public String toDefaultValue(Schema p) {
+        if (p.getEnum() != null && !p.getEnum().isEmpty()) {
+            if (p.getDefault() != null) {
+                return "." + escapeText((String) p.getDefault());
+            }
+        }
         if (ModelUtils.isIntegerSchema(p) || ModelUtils.isNumberSchema(p) || ModelUtils.isBooleanSchema(p)) {
             if (p.getDefault() != null) {
                 return p.getDefault().toString();

modules/openapi-generator/src/test/java/org/openapitools/codegen/swift4/Swift4ModelEnumTest.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2018 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ * Copyright 2018 SmartBear Software
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.openapitools.codegen.swift4;
+
+import io.swagger.v3.oas.models.media.*;
+import io.swagger.v3.parser.util.SchemaTypeUtil;
+import org.openapitools.codegen.CodegenModel;
+import org.openapitools.codegen.CodegenProperty;
+import org.openapitools.codegen.DefaultCodegen;
+import org.openapitools.codegen.languages.Swift4Codegen;
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+import java.util.Arrays;
+import java.util.Collections;
+
+@SuppressWarnings("static-method")
+public class Swift4ModelEnumTest {
+    @Test(description = "convert a java model with an enum and a default value")
+    public void converterTest() {
+        final StringSchema enumSchema = new StringSchema();
+        enumSchema.setEnum(Arrays.asList("VALUE1", "VALUE2", "VALUE3"));
+        enumSchema.setDefault("VALUE2");
+        final Schema model = new Schema().type("object").addProperties("name", enumSchema);
+
+        final DefaultCodegen codegen = new Swift4Codegen();
+        final CodegenModel cm = codegen.fromModel("sample", model, Collections.singletonMap("sample", model));
+
+        Assert.assertEquals(cm.vars.size(), 1);
+
+        final CodegenProperty enumVar = cm.vars.get(0);
+        Assert.assertEquals(enumVar.baseName, "name");
+        Assert.assertEquals(enumVar.dataType, "String");
+        Assert.assertEquals(enumVar.datatypeWithEnum, "Name");
+        Assert.assertEquals(enumVar.name, "name");
+        Assert.assertEquals(enumVar.defaultValue, ".VALUE2");
+        Assert.assertEquals(enumVar.baseType, "String");
+        Assert.assertTrue(enumVar.isEnum);
+    }
+}