Xbasic

node_request Function

Syntax

C node_request(C nodeService ,P pData [,L flagRestartNode [,L flagShowCommandWindow [,L flagAllowDebug ]]])

Arguments

nodeService

Name of the node service to run.

pData

Pointer to parameters to pass to the node service.

flagRestartNode

.t. or .f. value. Default .f.

Flag indicating whether or not the node server should be restarted when node_request is called. .t. restarts the node server. Restarting the node server can be useful for debugging purposes. flagRestartNode should be set to .f. in a production environment.

flagShowCommandWindow

.t. or .f. value. Default .f.

Show the command window for the node service handler (allows developer to see feedback using console.log() in the handler).

flagAllowDebug

.t. or .f. value. Default .f.

Enable node debugger (requires that the node debugger be launched).

Description

Calls a node service from Xbasic. Returns a JSON string.

The node_request function calls a node service for a web project. The web project must include a 'node_services' folder with the named node service. If the service is not present in the project, you will receive an error from node.

Below is an example call - it assumes a node service called 'eval' that reads javascript to execute from a 'content' property, then returns the result.

dim req as p
dim req.content as c = "1+1"
? node_request("eval",req)
= {"_id":"d18fa451-5c15-4cbf-8085-92fe24890e4d","error":"command eval was not recognized for command d18fa451-5c15-4cbf-8085-92fe24890e4d","result":null}

Add a node_services to the projects 'node' subfolder - save a file called 'eval.js' that has the following contents:

exports.handler = function(packet,response,sendResponse) {
	var e;
	var attachments = null;
	try {
	    response.result = eval(packet.content);
	    if( Buffer.isBuffer(response.result) ) {
	    	attachments = [{ name : 'data' , type : 'binary' , data : response.result }];
	    	response.result = 'binary data in attachment';	    	
	    }
	} catch( e ) {
	    response.error = e.message;
	}
	sendResponse(response,attachments);
};

The node service handler consumes a 'packet' that contains the parameters for the command. In this case, the parameter required is called "content", and gets evaluated, data is returned in a result parameter.

With 'node_services/eval.js' defined, now our example should work, notice that the result of evaluation is in a field called 'result', notice also that 'error' is blank.

dim req as p
dim req.content as c = "1+1"
? node_request("eval",req)
= {"_id":"d21a4938-d8bd-455f-9e82-e70bcc675316","error":"","result":2}

An example of a valid request with a handled error would be to pass a javascript expression that is invalid.

dim req as p
dim req.content as c = "1+"
? node_request("eval",req)
= {"_id":"4bee3d41-7816-4f0c-8b3f-ca853fa2ef0c","error":"Unexpected end of input","result":null}

Automatic Node Restart 

If you edit a Node Service, Alpha Anywhere will automatically set flagRestartNode to .T. in Live and Working Preview. If Node is not restart, any changes made to a Node Service will not be detected.