Hi all,
I have a weird issue where I use two instances of the same object and call
functions with callbacks from within these. At one stage one of the
functions called from object 2 is calling back object 1 instead.
*Background*
I am trying to build a control flow library that allows you to specify a
sequence of functions to be called and to branch based on conditions.
The concept is that you pass the library a flow [a,b,c], which then
executes functions a, b and c, passing the output values between them by
calling back to the FlowProcessor, which then calls the next function in
line, etc.
*Issue*
It all worked very well, until I added branching. Think this pseudocode:
[a,b, {IF value=1 THEN [a,a,a] ELSE [b,b,b]}, c], encapsulating the IF in
an object. Suppose value is 1, then the total flow should now be this:
[a,b,[a,a,a], c]. The second [a,a,a] flow is executed by instantiating a
new FlowProcessor object, which should then run to the end and return the
result into the first flow.
The weird thing happens next: After calling a in the second FlowProcessor,
a calls back into the FIRST FlowProcessor object. My question is why?
*Code*
var FlowProcessor = function (id, flow, data, finalCallback) {
this.id = id;
this.input = data;
this.flow = flow;
this.counter = 0 - 1;
this.flowLength = this.flow.length;
console.log(this.id, 'New FlowProcessor instance');
this.nextFlow = function (data) {
this.counter++;
if (this.counter < this.flow.length) {
switch (typeof (this.flow[this.counter])) {
case 'object':
this.parseObject(data, this.flow[this.counter], function (result) {
console.log('Object Parser called back');
this.nextFlow(result);
});
break;
default:
console.log(this.id, 'is calling function');
this.flow[this.counter](this.id, data, function (result) {
console.log(this.id, 'has been called back with result', result);
this.nextFlow(result);
});
}
} else {
finalCallback(data);
}
};
this.parseObject = function (data, obj, callback) {
switch (obj.type) {
case 'if':
if (eval(obj.condition)) {
console.log('Starting SubFlow (2)');
var o = new FlowProcessor(2, obj.flowTrue, data, function (result) {
console.log('Received Callback from SubFlow');
callback(result);
});
o.startFlow();
} else {
var o = new FlowProcessor(2, obj.flowFalse, data, function (result) {
callback(result);
});
o.startFlow();
}
break;
default:
callback(data);
}
};
this.startFlow = function () {
this.nextFlow(this.input);
}
return this;
}
var fp = FlowProcessor(1, [a, b, {type: 'if', condition: 'data<200',
flowTrue: [a,a,a], flowFalse: [b,b,b]}, c], 1, function (result) {
console.log(result);
});
fp.startFlow();
function a(id, a, callback) {
console.log(id, 'executing a');
callback(a + 10);
}
function b(id, a, callback) {
console.log(id, 'executing b');
callback(a + 20);
}
function c(id, a, callback) {
console.log(id, 'executing c');
callback(a + 30);
}
Output:(the first number in the line shows the FlowProcessor ID). The issue
is highlighted in red.
1 'New FlowProcessor instance'
1 'is calling function'
1 'executing a'
1 'has been called back with result' 11
1 'is calling function'
1 'executing b'
1 'has been called back with result' 31
Starting SubFlow (2)
2 'New FlowProcessor instance'
2 'is calling function'
*2 'executing a' //Flow 2 has called function a and executes it, then calls
callback1 'has been called back with result' 41 // Flow 1 receives the
callback??*
1 'is calling function'
1 'executing c'
1 'has been called back with result' 71
71
What am I doing wrong?
Thanks a lot,
Phil
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