Getting return value from JavaScript in UIWebView

Question

I want to fetch JavaScript return value in my ViewController,

The problem is that, if there is small amount of data like String, I'm getting it.

But if there is large data like JSON object,It's showing nil.

When I call same JS function in Safari > Develop > iOS simulator, it's giving JSON object after 1-2 secs.

Here is my code:

var value = IBwebView.stringByEvaluatingJavaScriptFromString("get_small_string()")
println(value)   //Printing value

but this prints nil,

var value = IBwebView.stringByEvaluatingJavaScriptFromString("get_JSON()")
println(value)   //Printing nil

anyone knows how can I fetch big size JS return value in iOS object?

Is it not possible to use the NSURL classes to fetch the JSON? Otherwise you are at the mercy of connection speeds and server response times. My only other thoughts are whether you can use a JSVirtualMachine, like I've done in this Playground where all JS is local. — sketchyTech
– sketchyTech, Commented Jun 5, 2015 at 7:22

Zaid Pathan · Accepted Answer · 2015-06-09 11:55:52Z

4

This solve my problem,

var value = IBwebView.stringByEvaluatingJavaScriptFromString("get_JSON()")

var err:NSError?
var obj:AnyObject? = NSJSONSerialization.JSONObjectWithData(value!.dataUsingEncoding(NSUTF8StringEncoding)!, options:nil, error:&err)

if let items = obj as? NSDictionary {
var data1:String = items.objectForKey("data1") as? String
var data2:String = items.objectForKey("data2") as? String
var data3:String = items.objectForKey("data3") as? String
}

answered Jun 9, 2015 at 11:55

Zaid Pathan

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oiledCode · Accepted Answer · 2015-06-08 07:01:45Z

2

As soon as you will return an object it will not work, what you can try instead is to return a stringified version of your object

JSON.stringify(yourObject);

And parse this string on the native side.

answered Jun 8, 2015 at 7:01

oiledCode

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1 Comment

ArunGJ Over a year ago

Thanks it worked. I was trying to fetch parsed object and it didn't work.

Santu C · Accepted Answer · 2015-06-05 06:47:43Z

0

If your java script method "get_JSON()" return more than 10 MB data then its not allowed by stringByEvaluatingJavaScriptFromString method.

Or If it take more than 10 sec to process output ,in that case you will be get nil value as output.

answered Jun 5, 2015 at 6:47

Santu C

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5 Comments

Zaid Pathan Over a year ago

there is only text data, so obviously less than 1MB, It's taking 1-2 sec in Safari > Develop > iOS simulator, as I mentioned.

Santu C Over a year ago

Where you called this method ?

Zaid Pathan Over a year ago

I called this method on one button's IBAction, I am pressing button after page completely loaded.

Zaid Pathan Over a year ago

Sorry, but it is confidential.

Santu C Over a year ago

then only last one suggestion , you may try to call this method within webviewdidfinish delegate

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