JavascriptCore: pass javascript function as parameter in JSExport

Question

JavascriptCore is a new infrastructure supported in iOS7. We can use the JSExport protocol to display parts of the objc class for JavaScript.

In javascript, I tried passing a function as a parameter. Similar:

function getJsonCallback(json) {
        movie = JSON.parse(json)
        renderTemplate()
}
viewController.getJsonWithURLCallback("", getJsonCallback)

In my objc viewController, I defined my protocol:

@protocol FetchJsonForJS <JSExport>
 - (void)getJsonWithURL:(NSString *)URL
               callback:(void (^)(NSString *json))callback;
 - (void)getJsonWithURL:(NSString *)URL
         callbackScript:(NSString *)script;
@end

In javascript, viewController.getJsonWithURLCallbackScript works, however, viewController.getJsonWithURLCallback does not work.

Is there an error that I used in JSExport? thank.

Answer 1

, Objective-C NSString arg, javascript , , , viewController.getJsonWithURLCallback("", getJsonCallback) - , undefined '

javascript.

Objective-C, JSValue.

( ):

TestHarnessViewController.h:

#import <UIKit/UIKit.h>
#import <JavaScriptCore/JavaScriptCore.h>

@protocol TestHarnessViewControllerExports <JSExport>
- (void)getJsonWithURL:(NSString *)URL callback:(JSValue *)callback;
@end

@interface TestHarnessViewController : UIViewController <TestHarnessViewControllerExports>
@end

TestHarnessViewController.m: ( copy/paste, - ):

#import "TestHarnessViewController.h"

@implementation TestHarnessViewController {
    JSContext *javascriptContext;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    javascriptContext  = [[JSContext alloc] init];
    javascriptContext[@"consoleLog"] = ^(NSString *message) {
        NSLog(@"Javascript log: %@",message);
    };
    javascriptContext[@"viewController"] = self;

    javascriptContext.exception = nil;
    [javascriptContext evaluateScript:@"
        function getJsonCallback(json) {
            consoleLog(\"getJsonCallback(\"+json+\") invoked.\");
            /* 
            movie = JSON.parse(json); 
            renderTemplate(); 
            */
        } 

        viewController.getJsonWithURLCallback(\"\", getJsonCallback);
    "];
    JSValue *e = javascriptContext.exception;
    if (e != nil && ![e isNull])
        NSLog(@"Javascript exception occurred %@", [e toString]);
}

- (void)getJsonWithURL:(NSString *)URL callback:(JSValue *)callback {
    NSString *json = @""; // Put JSON extract from URL here
    [callback callWithArguments:@[json]];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end