JS views on iOS

[Matija Alanović]

Hi!

How would I go about supporting Javascript views in an iOS application? Following the instructions on https://github.com/couchbase/couchbase-lite-ios/wiki/JavaScript-Views just leaves me with a bunch of linker errors.

Thanks in advance,
Matija Alanovic

[J. Chris Anderson]

On Monday, May 19, 2014 7:09:55 AM UTC-7, Matija Alanović wrote:

Hi!

How would I go about supporting Javascript views in an iOS application? Following the instructions on https://github.com/couchbase/couchbase-lite-ios/wiki/JavaScript-Views just leaves me with a bunch of linker errors.

Here is an example of how we do it within the PhoneGap plugin -- this should be similar enough to the code you want that it helps to copy from.

https://github.com/couchbaselabs/Couchbase-Lite-PhoneGap-Plugin/blob/master/src/ios/CBLite.m

Are you targetting iOS 6 (and shipping your own JS) or just using the built-in JavaScriptCore from iOS 7?

Chris

[Matija Alanović]

Thanks Chris!

I'll check it out tomorrow.
I'm only targeting iOS 7 so I'll be using the built-in JavaScriptCore.

[Matija Alanović]

Hi!

I looked at the code you provided. It's essentially the same thing I'm using and it doesn't work for me. I get a lot of linker errors like this:

Undefined symbols for architecture i386:
  "_JSContextGetGlobalObject", referenced from:
      -[CBLJSViewCompiler init] in CBLJSViewCompiler.o

It does that for every call to JavaScriptCore API. I don't really get why - shouldn't the old C JavaScriptCore API still be available on iOS 7, although the Objective-C wrapper functions can also be used?

[Matija Alanović]

I managed to get this working on a clean project, so it was a project-related problem. Maybe because I was using Cocoapods?

However, I'm now having problems accessing the views. What's the view naming scheme I should use?

This code doesn't return a view:
CBLView *myView = [self.database existingViewNamed:@"designdocumentname/viewname"];

[Matija Alanović]

Let me describe what I achieved and what doesn't work in a bit more detail.

I've got a working Javascript view on Cloudant. It's called "messages" and it's in a design document with an ID "_design/desdoc". I'd like to use it on iOS too. Here's what I do in the iOS application:
1. Set the view compiler to Javascript view compiler: CBLRegisterJSViewCompiler();
2. Get the view by its name: CBLView *myView = [self.database existingViewNamed:@"desdoc/messages"];
3. Try logging the view to see if the previos call returned anything: NSLog(@"view: %@", myView);

Unfortunately, only "view: (null)" is logged.

Is there anything I'm missing? Am I referencing the view by the correct name?

I can print the view's map function using this code:
NSLog(@"map function: %@", [self.database existingDocumentWithID:@"_design/desdoc"][@"views"][@"messages"][@"map"]);
Is there perhaps a way to feed this string to the compiler manually? I see there is a method named compileMapFunction in CBLJSViewCompiler, but it seems to be private.

[Jens Alfke]

On May 21, 2014, at 12:52 AM, Matija Alanović <mat...@infinum.hr> wrote:

I've got a working Javascript view on Cloudant. It's called "messages" and it's in a design document with an ID "_design/desdoc". I'd like to use it on iOS too.

Only the REST API looks up and compiles view source code from design documents. If you’re using the native API you’ll have to do it yourself. Once you have the JS source code, call

CBLMapBlock mapBlock = [[CBLView compiler] compileMapFunction: mapSource language: @"javascript”];

Then you can use that block to register the view’s map function.

I didn’t expect people to use JS views in native apps, to be honest; this feature was implemented for use with PhoneGap. The performance is going to be a lot worse than a native function, so IMHO it’s worth the effort to rewrite your map function in Objective-C.

—Jens

[Matija Alanović]

Thanks Jens, that was the line I was looking for!

I can't abandon JS views so this is my only option.

Thank you once again for your help.

This feature could be better documented though.

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[Julián Astrada]

Hi Matija, can you please tell me what framework are you using? I tried compiling a JavaScriptCore framework from Ejecta project or using a compiled one but I keep getting this same errors:

Undefined symbols for architecture i386:

  "_OBJC_CLASS_$_JSContext", referenced from:

objc-class-ref in AppDelegate.o

Thats when I call JSContext to start using a JavaScript.

[Jens Alfke]

On Feb 3, 2015, at 6:36 AM, Julián Astrada <astrad...@gmail.com> wrote:

Hi Matija, can you please tell me what framework are you using? I tried compiling a JavaScriptCore framework from Ejecta project or using a compiled one but I keep getting this same errors:

FYI: There's no need to compile JavaScriptCore unless your app needs to run on iOS 6.

JavaScriptCore is available as a public system framework on iOS 7+ and Mac OS, so you can just link against it.

—Jens

[Julián Astrada]

How do you link against it? What you mean? It is not available in the "Linked frameworks and libraries" list. And just adding the #import <JavaScriptCore/JavaScriptCore.h> doesn't fix it.

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[Jens Alfke]

On Feb 3, 2015, at 9:52 AM, Julián Astrada <astrad...@gmail.com> wrote:

How do you link against it? What you mean? It is not available in the "Linked frameworks and libraries" list. And just adding the #import <JavaScriptCore/JavaScriptCore.h> doesn't fix it.

You add it under Build Phases:

If you don't see it there, make sure your target is configured to use a current SDK (iOS 7+).

—Jens

[Julián Astrada]

Jens

First of all, thanks for your time. I was using iOS 8.2 and it wasn't there :( I just installed Xcode 6.2 beta 5 and it's there and works perfectly fine in the test application I did. I don't know if I messed up my previous xcode or beta 4 didn't include it.... It suspect it was me. 

Once again, thank you very much Jens!!

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