EWD 3 Training Course Part 9: Complex QEWD Messages and Responses

Copyright © 2016 M/Gateway Developments Ltd
EWD 3 Training Course
Part 9
Complex QEWD messages and
responses
Rob Tweed
Director, M/Gateway Developments Ltd
Twitter: @rtweed

Sending complex messages
• So far we've just sent the simplest
message possible:
– Only has a type property, and no additional
content or payload
• Messages can be as big and as complex
as you like
– Just JavaScript objects

• Define the content or payload in the
message object's params property
var messageObj = {
type: 'login',
params: {
username: $('#username').val(),
password: $('#password').val()
}
};
EWD.send(messageObj, callbackFn);

Handling Complex Messages
• In back-end handler, params available via
messageObj.params:
login: function(messageObj, session, send, finished) {
var username = messageObj.params.username;
if (username === '') {
finished({error: 'You must enter a username');
return;
}
var password = messageObj.params.password;
if (password === '') {
finished({error: 'You must enter a password');
return;
}
// …etc
}

• Params can be as complex an object as
you wish
var messageObj = {
type: 'complex',
params: {
foo: 'bar',
subObj: {
hello: 'world',
name: 'rob'
},
arr: ['a', 'b', 'c']
}
};

you wish
var messageObj = {
type: 'complex',
params: {
foo: 'bar',
subObj: {
hello: 'world',
name: 'rob'
},
arr: ['a', 'b', 'c']
}
};
At back-end:
var name = messageObj.params.subObj.name;

you wish
var messageObj = {
type: 'complex',
params: {
foo: 'bar',
subObj: {
hello: 'world',
name: 'rob'
},
arr: ['a', 'b', 'c']
}
};
At back-end:
var b = messageObj.params.arr[1];

Returning Complex Responses
• The response object returned by the back-
end handler's send() or finished() functions
can be as complex as you want
• Be careful with the response size:
– Can significantly slow down ewd-qoper8
– The larger the response, the longer it takes
for Express to return it to the browser or client

finished({
foo: 'bar',
myObj: {
hello: 'world',
name: 'Rob'
}
myArr: ['a','b','c']
});

finished({
foo: 'bar',
myObj: {
hello: 'world',
name: 'Rob'
}
myArr: ['a','b','c']
});
Accessed in browser-side
response handler as:
responseObj.message.myObj.name
In both EWD.send()'s callback
and Pub/Sub handler

EWD 3 Training Course Part 9: Complex QEWD Messages and Responses

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EWD 3 Training Course Part 9: Complex QEWD Messages and Responses