Creating block in Swift is not working

Question

I am trying to Create Block in Swift.

I have created class and declared block like this

typealias JSONParserBlock = (dict:NSDictionary?,error:NSError?) -> Void

Variable declaration:

var block: JSONParserBlock!

and Function:

func Getdata(WebService: String, RequsetedParameter Param:NSDictionary?, BLOCK: JSONParserBlock!) -> Void
{}

But my problem is when I call this function from another class, this function does not execute

Function call is like this:

var objJsonParser:JsonParser?

objJsonParser?.Getdata(str as String, RequsetedParameter:Dictionary, BLOCK:
    { (dict, error) in
        print("success")
})

Custom class code

import UIKit

class JsonParser: NSObject,NSURLConnectionDelegate
{
    typealias JSONParserBlock = (dict:NSDictionary?,error:NSError?) -> Void

    var block: JSONParserBlock!
    var Data:NSMutableData?=nil
    var delegate:JsonParserDelegate?
    var DICT:NSDictionary!
    var error: NSErrorPointer=nil
    func Getdata(WebService: String, RequsetedParameter Param:NSDictionary?, BLOCK: JSONParserBlock!) -> Void
    {
        self.block=BLOCK;
        Data = NSMutableData()
        let urlPath: String = "http://192.168.13.2/freshbakala/admin/json/GetCategory.php"
        let url: NSURL = NSURL(string: urlPath)!
        let request: NSURLRequest = NSURLRequest(URL: url)
        let connection: NSURLConnection = NSURLConnection(request: request, delegate: self, startImmediately: true)!
        connection.start()
    }

    func connection(didReceiveResponse: NSURLConnection!, didReceiveResponse response: NSURLResponse!)
    {
        self.Data = NSMutableData()
    }
    func connection(connection: NSURLConnection!, didReceiveData data: NSData!)
    {
        self.Data?.appendData(data)
    }
    func connectionDidFinishLoading(connection: NSURLConnection!)
    {
        let error:NSError
        let jsonresult:NSDictionary
        print("Response is received")
        do
        {
            jsonresult = try NSJSONSerialization.JSONObjectWithData(self.Data!, options: NSJSONReadingOptions.MutableContainers) as! NSDictionary
            print(jsonresult)
            block(dict: jsonresult,error: nil)

        }
        catch
        {

        }

    }
}

Could you show whole code of this two classes ?

Błażej
– Błażej

2016-04-25 13:04:09 +00:00
Commented Apr 25, 2016 at 13:04 — Błażej
– Błażej, Commented Apr 25, 2016 at 13:04

Community · Accepted Answer · 2017-05-23 12:23:56Z

1

Another problem, in addition to the issue pointed out by Mrwerdo is that this code:

var objJsonParser:JsonParser?

objJsonParser?.Getdata(str as String, RequsetedParameter:Dictionary, BLOCK: {
    (dict, error) in
    print("success")
})

doesn't actually do anything and won't complain because objJsonParser is nil unless you assign something to it and the ? in the invocation means that GetData will do nothing because the object is nil.

edited May 23, 2017 at 12:23

CommunityBot

11 silver badge

answered Apr 25, 2016 at 14:01

JeremyP

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Comments

Mrwerdo · Accepted Answer · 2016-04-25 13:08:34Z

1

You need to call the closure in the GetData function. Something like this should do:

func Getdata(WebService: String, RequsetedParameter Param:NSDictionary?, BLOCK: JSONParserBlock!) -> Void
{
  let dict: NSDictionary? = nil    // set these to something meaningful
  let error: NSError? = nil
  BLOCK(dict: dict, error: error)  // call the closure
}

answered Apr 25, 2016 at 13:08

Mrwerdo

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1 Comment

JeremyP Over a year ago

Yes, BLOCK is just a parameter to the function. The function body is empty, so the block does not get executed.

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