How to transfer a JSValueRef into a JavaScript var from Objective-C

Question

Using JavaScriptCore, if I have an NSString in Objective-C like this:

NSString *objcName = @"Kristof";

and a JSGlobalContextRef context called jsContextRef.

How do I transfer the Objective-C value of objcName into a named JavaScript variable in the jsContextRef? I was thinking along the lines of:

JSStringRef jsNameRef = JSStringCreateWithUTF8CString([objcName UTF8String]);
JSValueRef jsValueRef = JSValueMakeString(jsContextRef, jsNameRef);

Let's say the variable name will be "jsName". I need a couple more calls (or maybe even one call), something like:

// This part is pseudo-code for which I would like to have proper code:
JSValueStoreInVarWithName(jsContextRef,"jsName",jsValueRef);

so that in the end this JavaScript will evaluate correctly when called like this in Objective-C:

NSString *lJavaScriptScript = @"var jsUppercaseName = jsName.toUpperCase();";
JSStringRef scriptJS = JSStringCreateWithUTF8CString([lJavaScriptScript UTF8String]);
JSValueRef exception = NULL;
JSValueRef result = JSEvaluateScript(jsContextRef, scriptJS, NULL, NULL, 0, &exception);

Answer 1

I found the answer in the sample code for JavaScriptCoreHeadstart, more specifically the JSWrappers.m file. It has this method:

/* -addGlobalStringProperty:withValue: adds a string with the given name to the
 global object of the JavaScriptContext.  After this call, scripts running in
 the context will be able to access the string using the name. */
- (void)addGlobalStringProperty:(NSString *)name withValue:(NSString *)theValue {
    /* convert the name to a JavaScript string */
    JSStringRef propertyName = [name jsStringValue];
    if ( propertyName != NULL ) {
        /* convert the property value into a JavaScript string */
        JSStringRef propertyValue = [theValue jsStringValue];
        if ( propertyValue != NULL ) {            
            /* copy the property value into the JavaScript context */
            JSValueRef valueInContext = JSValueMakeString( [self JSContext], propertyValue );
            if ( valueInContext != NULL ) {                
                /* add the property into the context's global object */
                JSObjectSetProperty( [self JSContext], JSContextGetGlobalObject( [self JSContext] ),
                                propertyName, valueInContext, kJSPropertyAttributeReadOnly, NULL );
            }
            /* done with our reference to the property value */
            JSStringRelease( propertyValue );
        }
        /* done with our reference to the property name */
        JSStringRelease( propertyName );
    }
}

which is exactly what I needed. The code for the jsStringValue method is in NSStringWrappers.m in the same project and is:

/* return a new JavaScriptCore string value for the string */
- (JSStringRef)jsStringValue {
    return JSStringCreateWithCFString( (__bridge CFStringRef) self );
}

This seems to work.