Level 27
@tutanramon Why are you binding the existing indicator to the service container? What's wrong with invoking it directly?
foreach ($this->getIndicators() as $indicator) {
$finalScore += $indicator->buyScore();
}
May 5, 2021
7
Level 3
Dynamic binding implementations
I am planning to write a (small) stock analyzer. I want to check several technical indicators using webservices.
My idea is to have a IndicatorInterface with a couple of methods like fetchData(), evaluate() and buyScore() or something like that.
I got 3 classes right now
class RSI implements IndicatorInterface{} //Relative Strength Index
class SMA implements IndicatorInterface{} //Simple Moving Average
class DMI implements IndicatorInterface{} //Directional Movement Index
The plan is to have around 20 such class implementations. Thanks to the IndicatorInterface, each class has at least a method to collect the data, one to analyze it and one to give an buyScore.
The next step is to build strategies. A Strategy consists of one or more technical indicators (the classes above) with different thresholds etc. I want to store the strategies in the database and then run them.
So, for instance, strategy A: first run SMA, output should be 0.4 at least. If so, continue to DMI etc. etc.
In my Strategy Class, I now do this (part pseudo code):
public method run()
{
$finalScore = 0;
foreach ($this->getIndicators() as $indicator) {
App::bind('IndicatorInterface', 'App\Indicators\' . $indicator);
$indicator = App::make('IndicatorInterface');
$finalScore += $indicator->buyScore();
return $finalScore;
}
}
I am wondering if this is the way to go. Or do I need to use a different approach?
Thanks.
Level 3
Hi @corvs
I am new to the interface concept and thought i was a nice way to learn this. Thanks for helping me.
$this->getIndicators() gives a collection of indicators linked to the strategy.... How can I invoke the class related to the indicator?
Level 27
@tutanramon Just to clarify things, are we talking about an Eloquent relationship here? What does getIndicators() return? Just strings that represent the names (RSI, SMA, ...)?
Level 3
Hi,
Yes, i have a model Strategy and a model Indicator.
class Strategy extends Model{
public function indicators()
{
return $this->hasMany("App\Indicator");
}
// etc.
}
So, it's not getIndicators(), but indicators().
And the Indicator model contains the name of the class, ie App\Indicators\RSI and some threshold values.
Level 27
@tutanramon Alright. You may consider using STI (single table inheritance) for that, since you already have a "type" column anyway. It's pretty straightforward and if you are done setting it up you are able to iterate a strategie's indicators as mentioned above. There is a well documented and easy to use package from Caleb:
Level 3
Thanks again @CORVS.
I was reading last night about factory design pattern. I rewrote some of the code and now have a IndicatorFactory class which returns a new instance of a given indicator. So, the whole binding part is gone now. I just loop over the collection of Indicators, initiate new instances using the new factory and make some calculations.
Thanks to the contract (interface class) I now can easily add new indicators. I think this is a good approach, don't you?
I will also take a look at the package you suggested. Maybe that's even better. Thanks.
Level 27
I think this is a good approach, don't you?
Yes. The STI approach mentioned above is kinda similar to a factory pattern.
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