Update README.md

Author: tezpark

README.md

@@ -114,6 +114,43 @@ $(SRCROOT)/Carthage/Build/iOS/SendBirdSDK.framework
 
 > __Note__: The SendBirdUIKit Carthage built created in the latest Swift version. So, if the latest Swift environment is not configured, you need to copying the framework into the project manually.
 
+#### Unknown attribute error handling
+In Xcode 11.3 or earlier, there is a problem that build is impossible due to the following two errors.
+
+```basg
+- Unknown attribute '_inheritsConvenienceInitializers'
+- Unknown attribute '_hasMissingDesignatedInitializers'
+```
+
+This is due to the two annotation processing newly applied by Apple's Swift, and an error occurs because it is not a built-in function in Xcode 11.3 or earlier.
+
+If this problem occurs, you can use the Framework normally after removing annotation by referring to the following procedure. 
+
+This method removes the annotations that have problems in the swiftinterface that is automatically generated in the framework by executing the script in the build step in advance.
+
+1. Open the `edit scheme` menu of the project target.
+
+2. Select the `Build > Pre-actions` menu and add `new run script action`
+
+3. After adding the script below, select the target to apply the script.
+
+```bash
+# Cocoapods
+if [ -d "${PROJECT_DIR}/Pods/SendBirdUIKit" ]; then
+    find ${PROJECT_DIR}/Pods/SendBirdUIKit/SendBirdUIKit.framework/Modules/SendBirdUIKit.swiftmodule/ -type f -name '*.swiftinterface' -exec sed -i '' s/'@_inheritsConvenienceInitializers '// {} +
+    find ${PROJECT_DIR}/Pods/SendBirdUIKit/SendBirdUIKit.framework/Modules/SendBirdUIKit.swiftmodule/ -type f -name '*.swiftinterface' -exec sed -i '' s/'@_hasMissingDesignatedInitializers '// {} +
+fi
+
+# Carthage
+if [ -d "${PROJECT_DIR}/Carthage/Build/iOS/SendBirdUIKit.framework" ]; then
+    find ${PROJECT_DIR}/Carthage/Build/iOS/SendBirdUIKit.framework/Modules/SendBirdUIKit.swiftmodule/ -type f -name '*.swiftinterface' -exec sed -i '' s/'@_inheritsConvenienceInitializers '// {} +
+    find ${PROJECT_DIR}/Carthage/Build/iOS/SendBirdUIKit.framework/Modules/SendBirdUIKit.swiftmodule/ -type f -name '*.swiftinterface' -exec sed -i '' s/'@_hasMissingDesignatedInitializers '// {} +
+fi
+```
+
+4. Now build & run and you can see that the problem is solved.
+
+
 ---
 
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