HTTP Request through JavaScriptCore in iOS7 - ios

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.

Answer 3

JSContext *context = [[JSContext alloc] init];
context[#"request"] = ^(NSString *url) {
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:url]
cachePolicy:NSURLRequestReloadIgnoringCacheData
timeoutInterval:10];
NSURLResponse *response = nil;
[request setHTTPMethod:#"GET"];
NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];
NSString *body = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
return body;
};
In JS:
var body = request(url);