topic scope issue, setting 'this' object for use later in ArcGIS JavaScript Maps SDK Questions

scope issue, setting 'this' object for use later

JamesCrandall — Sat, 11 Dec 2021 06:09:55 GMT

I'm falling short here and need some help. I need to ensure that 'this.fsTok' gets set at the startup before 'this.createServerSiteScratchLayer()' but it seems that no matter what fsTok is always undefined in the createServerSiteScratchLayer() function.

fsTok: null

startup: function(){
	this.fsTok = this.getFStokFromUrl();
        this.createServerSideScratchLayer();

},

getFStokFromUrl: function () {
             
	tok = ""
	var gp = new Geoprocessor("gpServiceURL/execute");
	var params = { "inSystem": "someInputParamValue"};
	gp.execute(params, retTok);
	function retTok(results) {
		tok = results[0].value;
	}

	return tok
  
},

createServerSideScratchLayer: function () {              
  this.serverSideScratchLayer = new FeatureLayer(this.config.applicationFeatureLayer + '?token=' + this.fsTok,
	  {
		  outFields: ["OBJECTID"]
	  });              
},‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: scope issue, setting 'this' object for use later

ManishPatel — Sat, 11 Dec 2021 06:09:58 GMT

Hi James Crandall,

The code looks correct, however it depends if your gp service is sync or async and whether the function waits till the response is received back.

Ideally, you can check if the response is received and put the createServerSiteScratchLayer() in the getFStokFromUrl function's response.

fsTok: null

startup: function(){
     this.fsTok = this.getFStokFromUrl();
        

},

getFStokFromUrl: function () {
             
     tok = ""
     var gp = new Geoprocessor("gpServiceURL/execute");
     var params = { "inSystem": "someInputParamValue"};
     gp.execute(params, retTok);
     function retTok(results) {
          tok = results[0].value;
          //this.fsTok = results[0].value; you can set this if you need to use it again
          this.createServerSideScratchLayer(tok);//or pass as parameter to the function
     }  
},

createServerSideScratchLayer: function (token) {              
  this.serverSideScratchLayer = new FeatureLayer(this.config.applicationFeatureLayer + '?token=' + token,
       {
            outFields: ["OBJECTID"]
       });              
},

Cheers,

Manish

If this answer solved your question or if you found it helpful please mark it accordingly to help others who have the same question.

Re: scope issue, setting 'this' object for use later

JamesCrandall — Thu, 29 Oct 2020 01:32:20 GMT

Thanks Manish,

I followed your approach but getting "this.createServerSideScratchLayer is not a function" error on this line,

this.createServerSideScratchLayer(tok);//or pass as parameter to the function

Re: scope issue, setting 'this' object for use later

ManishPatel — Sat, 11 Dec 2021 06:10:01 GMT

Can you try with this instead

createServerSideScratchLayer(tok)

You can try to debug the code and see if you are receiving the token and also if the function is approachable.

Or alternatively, you can move your code snippet in the response function instead.

getFStokFromUrl: function () {
             
     tok = ""
     var gp = new Geoprocessor("gpServiceURL/execute");
     var params = { "inSystem": "someInputParamValue"};
     gp.execute(params, retTok);
     function retTok(results) {
          tok = results[0].value;
          this.serverSideScratchLayer = new FeatureLayer(this.config.applicationFeatureLayer + '?token=' +tok 
,
       {
            outFields: ["OBJECTID"]
       });     
     }  
},

Try this if that helps.

Cheers,

Manish

Re: scope issue, setting 'this' object for use later

JamesCrandall — Thu, 29 Oct 2020 15:06:02 GMT

this works, thanks. Now it has uncovered an additional scope issue when I try to access this.serverSideScracthLayer from another function.

It's very difficult to inherit code from another developer that has written so many functions that separate out all of the logic. Plus I'm still not fully understanding scope and accessing/setting variables that can be used later on.

Re: scope issue, setting 'this' object for use later

ManishPatel — Thu, 29 Oct 2020 22:27:19 GMT

I am glad that worked out for you.

I understand when trying to inherit code from another developer it an always be challenging but I am sure you will find a way out 🙂

Regarding the scope issue, I usually either pass it as a parameter from function to function or create a global class that holds all the variables and reference it throughout the application.