use pod instead

example/ios/Runner.xcodeproj/project.xcworkspace/contents.xcworkspacedata

@@ -2,6 +2,6 @@
 <Workspace
    version = "1.0">
    <FileRef
-      location = "group:Runner.xcodeproj">
+      location = "self:">
    </FileRef>
 </Workspace>

example/lib/sign_auto_deduct_page.dart

@@ -96,16 +96,16 @@ class _SignAutoDeductPageState extends State<SignAutoDeductPage> {
 
   void _signAutoDeduct() {
     autoDeDuctWeChat(
-        appId: appId.text ?? "",
-        mchId: mchId.text ?? "",
-        planId: planId.text ?? "",
-        contractCode: contractCode.text ?? "",
+        appId: appId.text ,
+        mchId: mchId.text,
+        planId: planId.text ,
+        contractCode: contractCode.text,
         requestSerial: requestSerial.text ?? "",
-        contractDisplayAccount: contractDisplayAccount.text ?? "",
-        notifyUrl: notifyUrl.text ?? "",
-        version: version.text ?? "",
-        sign: sign.text ?? "",
-        timestamp: timestamp.text ?? "",
+        contractDisplayAccount: contractDisplayAccount.text,
+        notifyUrl: notifyUrl.text,
+        version: version.text,
+        sign: sign.text,
+        timestamp: timestamp.text,
         returnApp: '3');
   }
 }

example/pubspec.lock

@@ -73,7 +73,7 @@ packages:
       path: ".."
       relative: true
     source: path
-    version: "3.5.1"
+    version: "3.6.1+1"
   matcher:
     dependency: transitive
     description: