NodeJs promises returning too early - node.js

Question

I'm new to NodeJs and code I'm working with is using Q framework for promises.
And it seems that I don't understand the 'Q' framework too well, I'm running into a case when promises are returning too early.
Here is my code:
BridgeInfo.getBridgeInfo(exten)
.then(function processBridgeInfo(bridge_info) {
console.log("Nitesh -- bridge info is back, yay");
if (bridge_info !== undefined) {
conf_bridge = new VoxConfBridge(ari);
conf_bridge.init(bridge_info);
/**Add the bridge to the bridgeList**/
bridgeList[conf_bridge.bridge.id] = conf_bridge;
console.log("Bridge ID to register is "+ conf_bridge.bridge.id);
self.registerEvents(conf_bridge.bridge);
conf_bridge.registerUser(event, false, channel);
} else {
console.log("Unknown extension [" + exten + "] blocking it");
ChannelDriver.blockChannel(ari, channel.id);
}
})
.catch(function handleError(err) {
console.error("Nitesh -- [voxbridgemanager] error occured "+err);
});
The above code calls a function getBridgeInfo, this function is supposed to do some DB queries and return the result.
Here is the code in getBridgeInfo
BridgeInfo.getBridgeInfo = Q.async(function(bridge_identifier) {
console.log("Nitesh -- Getting the bridge info for ["+ bridge_identifier + "]");
if (bridge_identifier !== undefined) {
db.getConfBridgeProfile(bridge_identifier)
.then(function processBridgeProfile(result) {
if (result !== undefined) {
console.log("Nitesh -- Bridge Info is "+ JSON.stringify(result));
var bridge_info = new BridgeInfo();
bridge_info.init(result)
.then (function bridgeInfoInitDone() {
return bridge_info;
})
.catch( function handleError(err) {
console.error("Nitesh ---[bridgeInfoInit] Error is "+ err);
});
}
else {
console.log("Can't find any bridge profile for this identifier ["+ bridge_identifier + "]");
}
}, function handleError(err) {
console.error("Failed to retrieve bridgeInfo");
});
} else {
console.error("Received an invalid identifier");
}
});
**When I run this code, I see that in my main code,which calls getBrigeInfo, it hits its catch error handler even before getBRidgeInfo has executed completely, getBridgeInfo's SQL query results appear afterwards.
I think the way I'm using promises isn't being done correctly, any explanations please

Answer 1

Your missing the key part of what promises can do.
You should not need to do any catch statements in your getBridgeInfo. You should return the whole promise that gets the SQL data... and handle it in your first block of code BridgeInfo.getBridgeInfo(exten)
Assuming that db.getConfBridgeProfile(bridge_identifier); returns a promise
Example:
BridgeInfo.getBridgeInfo = function(bridge_identifier) {
console.log("Nitesh -- Getting the bridge info for ["+ bridge_identifier + "]");
if (bridge_identifier !== undefined) {
return Q.fcall(function () {
throw new Error("Received an invalid identifier");
});
}
return db.getConfBridgeProfile(bridge_identifier);
}
I've also seperated out your process query... keep things simple.
BridgeInfo.processBridgeProfile = function(result) {
if (result !== undefined) {
console.log("Nitesh -- Bridge Info is "+ JSON.stringify(result));
var bridge_info = new BridgeInfo();
return bridge_info.init(result);
}else{
return Q.fcall(function () {
throw new Error("Can't find any bridge profile for this identifier ["+ bridge_identifier + "]");
});
}
Return promises and handle the catch in the main function. Your getting stuck in handling a catch, the SQL results are not getting returned like they should.
Call:
BridgeInfo.getBridgeInfo(bridge_identifier).then(function(result){
return BridgeInfo.processBridgeProfile(result)
}).then(function(){
//Do the rest here
}).catch(function(){
//One catch to rule them all :)
});