How to obtain a value from DataSource?

[cladav85_removed]

I know the primary key fieldname and the primary key, and I want to know the value of another known fieldname in the DataSource. How do I do this?

I have tried with fetchData(Criteria criteria, DSCallback callback), (DSCallback code below)

SC.say(returnValue) shows the right value but when I use getValue() the return string is Empty.

package com.companyweb.client.ui.data;

import com.smartgwt.client.data.DSCallback;
import com.smartgwt.client.data.DSRequest;
import com.smartgwt.client.data.DSResponse;
import com.smartgwt.client.data.Record;
import com.smartgwt.client.util.SC;

public class CustomDSCallback implements DSCallback{

	private String returnValue = "";
	private String fieldNameToGet = "";
	
	
	
	public CustomDSCallback(String fieldNameToGet){
		this.fieldNameToGet = fieldNameToGet;
	}
	
	@Override
	public void execute(DSResponse response, Object rawData, DSRequest request) { 
		Record fetchedData = response.getData()[0];
		if(fetchedData != null) {
			returnValue = fetchedData.getAttribute(fieldNameToGet);
			SC.say(returnValue);		
}
		else
			SC.say("CustomDSCallback failed!");
	} 
	
	
	public String getValue() {
		return returnValue;
	}
	

}

[alius]

Hi,

You have to take into account that fetchData is asynchronous. This means that returnValue will be populated only after response will arrive. So following code will return empty string:

CustomDSCallback callback = new CustomDSCallback("myField");
dataSource.fetchData(criteria, callback);
SC.say("Current callback value: " + callback.getValue());

To prove it - assign initial value to returnValue:

private String returnValue = "NO VALUE";

Execution sequence will be like this:
a) created callback;
b) sent request to server;
c) printing "Current callback value" + callback.getValue()
... some time passes ...
d) response from server received
e) new value is assigned to returnValue (in execute() method)
f) printing returnValue (in execute() method)

Regards,
Alius

[cladav85_removed]

Thanks

but how should I do to accomplish what I want? (get one value from a datasource)

Hi,

You have to take into account that fetchData is asynchronous. This means that returnValue will be populated only after response will arrive. So following code will return empty string:

CustomDSCallback callback = new CustomDSCallback("myField");
dataSource.fetchData(criteria, callback);
SC.say("Current callback value: " + callback.getValue());

To prove it - assign initial value to returnValue:

private String returnValue = "NO VALUE";

Execution sequence will be like this:
a) created callback;
b) sent request to server;
c) printing "Current callback value" + callback.getValue()
... some time passes ...
d) response from server received
e) new value is assigned to returnValue (in execute() method)
f) printing returnValue (in execute() method)

Regards,
Alius

[alius]

You can access that value after response from server received and callback executed (after step e).

[cladav85_removed]

You can access that value after response from server received and callback executed (after step e).

I understand that, and I have tried with this code:

private boolean gotResponseFromServer = false;

...

	@Override
	public void execute(DSResponse response, Object rawData, DSRequest request) { 
...
		gotResponseFromServer = true;
...
	} 

	public boolean dataHasArrived() {
		return gotResponseFromServer;
	}

	
CustomDSCallback callback = new CustomDSCallback("myField");
dataSource.fetchData(criteria, callback);
while(!callback.dataHasArrived()){}
SC.say("Current callback value: " + callback.getValue());

But when this code is executed the browser stop working.