Pass NSDictionary from Javascript to Objective-c in JavascriptCore

Question

I'm using JavascriptCore in my app. Now, I'm passing some variables to the JSContext that can then be passed back to Objective-C. However, one of the variables, an NSDictionary, is not passing through correctly. I run the code below:

var evaluate = function(variables) {
    app.setDictionary(variables.dictionary);
}

This is a simple example that has these following methods set up in JSContext.

This is the setDictionary() method:

- (void)setDicationary:(NSDictionary *)dictionary {
    self.mutableDictionary = [dictionary mutableCopy];
}

This is variables.dictionary:

- (NSDictionary *)dictionary {
    return self.values;
}

And this is how I call evaluate():

JSValue *jsFunction = self.context[@"evaluate"];
JSValue *value = [jsFunction callWithArguments:@[self.variables]];

However, in the setDictionary method, I don't get an NSDictionary, but instead get a NSString containing [object Object].

Any ideas how I can solve this?

Please, add Objective-C code counterpart to the question.

Borys Verebskyi
– Borys Verebskyi

2017-03-28 10:52:39 +00:00
Commented Mar 28, 2017 at 10:52 — Borys Verebskyi
– Borys Verebskyi, Commented Mar 28, 2017 at 10:52
@BorisVerebsky I added it!

user4992124
– user4992124

2017-03-28 10:58:25 +00:00
Commented Mar 28, 2017 at 10:58 — user4992124
– user4992124, Commented Mar 28, 2017 at 10:58

Borys Verebskyi · Accepted Answer · 2017-03-28 11:10:53Z

1

Although JavaScriptCore automatically converts types between Objective-C or Swift and JavaScript, I suggest to implement explicit conversion. Automatic conversion doesn't always work as developer may expect. For example undefined is converted to @"undefined" in case, when NSString is used.

Try something like:

- (void)setDicationary:(JSValue *)jsDictionary {
    if ([jsDictionary isUndefined] || [jsDictionary isNull]) {
        jsDictionary = nil;
    }
    self.mutableDictionary = [jsDictionary toDictionary];
}

Note that JavaScript uses object as dictionary, so you should be very careful with argument that you passing to Objective-C code. Passing any system object will result to recursive conversion of that object to NSDictionary.

answered Mar 28, 2017 at 11:10

Borys Verebskyi

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