Discussion of article "How to call indicators in MQL5"

[MetaQuotes]

New article How to call indicators in MQL5 is published:

With new version of MQL programming language available not only the approach of dealing with indicators have changed, but there are also new ways of how to create indicators. Furthermore, you have additional flexibility working with indicator's buffers - now you can specify the desired direction of indexing and get exactly as many indicator's values as you want. This article explains the basic methods of calling indicators and retrieving data from the indicator's buffers.

In MQL5 there are several ways to call indicators, and they are mostly carried out using IndicatorCreate() and iCustom() functions. Moreover, these functions only return indicator handle, and further work on indicators is done through it. So what is a handle? How to deal with IndicatorCreate() and iCustom() functions? And how your expert will get indicator data? All these questions are covered in this article.

Author: KlimMalgin

[ts_]

useful article. thanks a lot.

[OldZ]

Good ++ 

Thanks.

[Andrew Petras]

Please explain.

In "Obtaining indicator handle using IndicatorCreate()"

Create an array

MqlParam params[];      // Array for storing indicator parameters

Without specifying the type, then change the array type as needed.

How does it work? Can it be used for any structures or only for this one? Is it possible to just change the type of an existing array?

[Rashid Umarov]

The array of parameters of MqlParam type is necessary for IndicatorCreate() function only when creating a handle. If you want to change something, you need to "kill" the current handle using IndicatorRelease and create a new one. Indicator "engine change" on the move is not provided.

[Andrew Petras]

But in the article, in the text.

   ***
   // Set the period of the slow MA
   params[0].type         =TYPE_INT;
   params[0].integer_value=21;
   ***

and following it.

   ***
   ArrayResize(params,2);
   // Step
   params[0].type         =TYPE_DOUBLE;
   params[0].double_value = 0.02;
   ***

nothing is deleted, the type is changed.....

[Rashid Umarov]

Let's take it on a catering level. A waiter places dishes on a tray and takes your order to you. Then he places another customer's food on the same tray and takes your order to him. Does this mean that you have the same meal as the other customer?

[Andrew Petras]

So, different dinners can only be on the waiter's tray. Okay, I'll experiment.

Are there any plans for arrays of mixed types, like [int][double]?

[Rashid Umarov]

Silent:

So, different dinners can only be on the waiter's tray. Okay, I'll experiment.

Are there no plans for arrays of mixed types, like [int][double]?

Use structures, see the example in the help - https://www.mql5.com/ru/docs/basis/types/casting#casting_structure:

Another example shows how you can organize your own function to get RGB (Red,Green,Blue) colour representation from colour type. To do this, we create two structures that have the same size but different internal composition. For convenience, let's add to the structure a function that returns colour in RGB representation as a string.

#property script_show_inputs
input color          testColor=clrBlue;// set the colour for testing
//--- structure for RGB colour representation
struct RGB
  {
   uchar             blue;          // blue colour component
   uchar             green;         // green colour component
   uchar             red;           // red colour component
   uchar             empty;         // this byte is not used
   string            toString();    // function to receive as a string
  };
//--- function to output the colour as a string
string RGB::toString(void)
  {
   string out="("+(string)red+":"+(string)green+":"+(string)blue+")";
   return out;
  }
//--- structure for storing the built-in type colour 
struct builtColor
  {
   color             c;
  };
//+------------------------------------------------------------------+
//| Script programme start function|
//+------------------------------------------------------------------+
void OnStart()
  {
//--- variable to store in RGB
   RGB colorRGB;
//--- variable for storing colour type
   builtColor test;
   test.c=testColor;
//--- converting two structures by copying their contents
   colorRGB=test;
   Print("color ",test.c," = ",colorRGB.toString());
//---
  }

[Andrew Petras]

Rosh:

Use structures, see the example in the help - https://www.mql5.com/ru/docs/basis/types/casting#casting_structure:

I understand more or less with structures, I'm interested in arrays.

Thanks.

[Rashid Umarov]

Silent:

I'm more or less clear with structures, I'm interested in arrays.

Thank you.

Make a structure and type an array of this type.