HTTP Request through JavaScriptCore in iOS7

Question

I am trying to use one of iOS7 new features, the JavaScriptCore Framework. I can successfully output a helloWorld string from Javascript, but what I'm interested in, is doing HTTP POSTs in Javascript and then pass the response to Objective-C. Unfortunately, when I'm creating an XMLHttpRequest object in Javascript, I get EXC_BAD_ACCESS (code=1, address=....).

Here is the Javascript code (hello.js):

var sendSamplePost = function () {
    // when the following line is commented, everything works,
    // if not, I get EXC_BAD_ACCESS (code=1, address=....)
    var xmlHttp = new XMLHttpRequest();
};

var sayHello = function (name) {
    return "Hello " + name + " from Javascript";
};

Here is the Objective-C code inside my ViewController:

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    JSContext *context = [[JSContext alloc] initWithVirtualMachine:[[JSVirtualMachine alloc] init]];

    NSString *scriptPath = [[NSBundle mainBundle] pathForResource:@"hello" ofType:@"js"];
    NSLog(@"scriptPath: %@", scriptPath);
    NSString *script = [NSString stringWithContentsOfFile:scriptPath encoding:NSUTF8StringEncoding error:nil];
    NSLog(@"script: %@", script);

    [context evaluateScript:script];

    JSValue *sayHelloFunction = context[@"sayHello"];
    JSValue *returnedValue = [sayHelloFunction callWithArguments:@[@"iOS"]];

    // this works!
    self.label.text = [returnedValue toString];


    JSValue *sendSamplePostFunction = context[@"sendSamplePost"];

    // this doesn't work :(
    [sendSamplePostFunction callWithArguments:@[]];
}

Could it be that HTTP Requests functionality is not provided in JavaScriptCore Framework? If yes, could I overcome this by using UIWebView's -stringByEvaluatingJavaScriptFromString:? What if I compiled and included in my project another Javascript Engine (e.g. V8)?

Answer 1

XMLHttpRequest is, as stated before, not part of JavaScript, but you still can wrap the iOS URLRequest so it's available in your JS.

in JSUtils.h

   @protocol UtilsExport;

   @interface JSUtils : NSObject <UtilsExport>
   @end

   @protocol UtilsExport <JSExport>
   - (void)get:(NSString *)url then:(JSValue *)jsCallback;
   @end

in JSUtils.m

#import "JSUtils.h"

- (void)get:(NSString *)url then:(JSValue *)callback {
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:url]
                                                           cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData
                                                       timeoutInterval:10];
    [request setHTTPMethod:@"GET"];
    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
        if ([data length] > 0 && error == nil) {
            [callback callWithArguments:@[[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding], @YES]];
        } 
    }];
}

Next, bind the instance to the JSContext somewhere in your code

JSContext *context = [[JSContext alloc] init];
context[@"utils"] = [[JSUtils alloc] init];

from your JS file, you can now call

utils.getThen('http://localhost/api/dashboard', function(resultString){
  console.log(resultString)
}

You could also use a block and bind it straight to the JSContext to get the same result.

Answer 2

My guess would be that HTTP Requests are not part of JavaScript Core, as it's really part of the browser, not the JavaScript Language.
I would assume that JavaScript core only includes what's in the ECMAScript definition.

If you want AJAX, then the WebView is the way to go.