add some method

ios/Classes/BaseCallback.swift

@@ -0,0 +1,27 @@
+//
+//  BaseCallback.swift
+//  flutter_openim_sdk
+//
+//  Created by willem on 2021/10/9.
+//
+
+import Foundation
+import OpenIMCore
+
+public class BaseCallback: NSObject, Open_im_sdkBaseProtocol {
+    
+    private let result:FlutterResult
+    
+    init(result:@escaping FlutterResult) {
+        self.result = result
+    }
+    
+    public func onError(_ errCode: Int, errMsg: String?) {
+        print("BaseResult: " + errMsg!)
+        safeMainAsync { self.result(FlutterError(code: "\(errCode)", message: errMsg, details: nil)) }
+    }
+    
+    public func onSuccess(_ data: String?) {
+        safeMainAsync { self.result(data) }
+    }
+}