Upgrading #Cordova apps from #UIWebView to #WKWebView

Cordova hybrid iOS apps are based on the idea of wrapping a web application in a UIWebView in order to serve it as an app resembling a native iOS app. Apple has informed all iOS developers that UIWebView will be deprecated, and that new, or updated apps must use WKWebView instead. The idea that UIWebView could bypass fundamental restrictions that Web users are used to, is certainly problematic, and it’s not surprising that Apple has taken this move.

However, if you’ve got a Cordova based app, and need to make an upgrade, then perhaps you may need to take cognisance of these new limitations, and the upgrade path.

So, first off, to do the basic upgrade, you need to run the following command

cordova plugins add cordova-plugin-wkwebview-engine

Then Make a modification to config.xml as follows;

<platform name=”ios”>
<preference name=”WKWebViewOnly” value=”true” />

<feature name=”CDVWKWebViewEngine”>
<param name=”ios-package” value=”CDVWKWebViewEngine” />
</feature>

<preference name=”CordovaWebViewEngine” value=”CDVWKWebViewEngine” />
</platform>

Then rebuild the app using

cordova build ios

That’s the basic upgrade path, but let’s dive deeper. One of the abilities of UIWebView was that you could make cross-origin requests without any restrictions. This is no longer possible in WKWebView, so you need to make sure that your AJAX requests are CORS compliant.

Assuming the API you are connecting to is not CORS enabled, and you have no direct control over it to make it CORS enabled, you will need to use a CORS proxy. One of the easiest ways to do this is via an API gateway using AWS.

Log in to AWS, and go to API Gateway. Press “Create API”, then “Build” beside HTTP API, then Add Integration -> HTTP. Set the URL endpoint to the root domain of the destination API that you are trying to call. Give the API a name and press “Next” Set Resource path to $default and press next. Press Next again, then Create.

Once created, click on the API, and press CORS on the left hand side. Press Configure. In Access-Control-Allow-Origin type * and press add. Do the same for Access-Control-Allow-Headers and Access-Control-Expose-Headers. For Access-Control-Allow-Methods select each method in turn, and press Add. Finally, Press Save.

You will now have an CORS-Enabled API endpoint, like https://xxxxxxx.execute-api.yyyyyyyyy.amazonaws.com that you can use to call the target API endpoint.

Then update your app source code, to change the domain to point at the AWS domain rather than the target API.

Before you compile, there is one last step; you have to add the following plugin:

cordova plugin add https://github.com/TheMattRay/cordova-plugin-wkwebviewxhrfix

What this does, is to set the origin header correctly within Cordova WKWebView, such that CORS will see it as a non-null origin, and will actually work.

Now, test your app, and hopefully you can now re-submit updates without apple complaining.

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