Learn use of Class in mql5

1. What is a Class?

A class in MQL5 is a blueprint for creating objects. It allows you to encapsulate data and methods that operate on that data. In MQL5, a class is defined using the class keyword and can have private, protected, and public sections for its members (variables and functions).

2. Basic Structure of a Class

Here’s a basic structure of a class in MQL5:

class MyClass
{
private:
   int privateVariable;

public:
   
   MyClass(int initialValue) {
       privateVariable = initialValue;
   }

   
   void SetValue(int newValue) {
       privateVariable = newValue;
   }

   
   int GetValue() {
       return privateVariable;
   }
};

3. Example: Using a Class to Manage Trading Settings

Let’s create a class that manages trading settings like lots, stop loss, and take profit.

class TradingSettings
{
private:
   double lots;
   int stopLoss;
   int takeProfit;

public:
   
   TradingSettings(double initialLots, int initialStopLoss, int initialTakeProfit)
   {
       lots = initialLots;
       stopLoss = initialStopLoss;
       takeProfit = initialTakeProfit;
   }

   
   void SetLots(double newLots)
   {
       lots = newLots;
   }

   
   double GetLots()
   {
       return lots;
   }

   
   void SetStopLoss(int newStopLoss)
   {
       stopLoss = newStopLoss;
   }

   
   int GetStopLoss()
   {
       return stopLoss;
   }

   
   void SetTakeProfit(int newTakeProfit)
   {
       takeProfit = newTakeProfit;
   }

   
   int GetTakeProfit()
   {
       return takeProfit;
   }
};


input double lotSize = 0.1;
input int slippage = 3;
input int stopLoss = 50;
input int takeProfit = 100;

TradingSettings tradingSettings(lotSize, stopLoss, takeProfit);

void OnStart()
{
    
    Print("Initial Lot Size: ", tradingSettings.GetLots());
    Print("Initial Stop Loss: ", tradingSettings.GetStopLoss());
    Print("Initial Take Profit: ", tradingSettings.GetTakeProfit());

    
    tradingSettings.SetLots(0.2);
    tradingSettings.SetStopLoss(100);
    tradingSettings.SetTakeProfit(200);

    
    Print("Updated Lot Size: ", tradingSettings.GetLots());
    Print("Updated Stop Loss: ", tradingSettings.GetStopLoss());
    Print("Updated Take Profit: ", tradingSettings.GetTakeProfit());
}

Explanation

1. Class Definition:

   • TradingSettings class has private variables for lots , stopLoss , and takeProfit .
   • Public methods are used to set and get these values.

2. Constructor:

   • The constructor initializes the class with default values when an object is created.

3. Methods:

   • Methods like SetLots , GetLots , etc., are used to interact with the private variables.

4. Usage:

   • In the OnStart() function of an EA, an object of TradingSettings is created and initialized.
   • The methods of the class are used to manipulate and retrieve trading settings.

This is a basic example to illustrate how to use classes in MQL5. Classes are powerful and can be used to manage more complex logic and data in your trading applications.

Now lets code another example for better understanding about creating a class class for candle patterns, hammer and spinning top

class CandlestickPatterns
{
private:
   double open;    
   double close;   
   double high;    
   double low;     

   
   double BodySize() {
       return MathAbs(close - open);
   }

   
   double UpperShadowSize() {
       return high - MathMax(open, close);
   }

   double LowerShadowSize() {
       return MathMin(open, close) - low;
   }

public:
   
   CandlestickPatterns(double openPrice, double closePrice, double highPrice, double lowPrice) {
       open = openPrice;
       close = closePrice;
       high = highPrice;
       low = lowPrice;
   }

   
   bool IsHammer() {
       double bodySize = BodySize();
       double lowerShadow = LowerShadowSize();
       double upperShadow = UpperShadowSize();

       if (bodySize == 0)
           return false;

       
       if (lowerShadow >= 2 * bodySize && upperShadow 0.1) {
           return true;
       }

       return false;
   }

   
   bool IsSpinningTop() {
       double bodySize = BodySize();
       double totalLength = high - low;
       double upperShadow = UpperShadowSize();
       double lowerShadow = LowerShadowSize();

       if (bodySize == 0 || totalLength == 0)
           return false;

       
       if (bodySize 0.3 && upperShadow >= bodySize * 0.5 && lowerShadow >= bodySize * 0.5) {
           return true;
       }

       return false;
   }
};


void OnStart()
{
    
    double openPrice = 1.1050;
    double closePrice = 1.1060;
    double highPrice = 1.1080;
    double lowPrice = 1.1040;

    
    CandlestickPatterns candle(openPrice, closePrice, highPrice, lowPrice);

    
    if (candle.IsHammer()) {
        Print("The candle is a Hammer.");
    } else {
        Print("The candle is not a Hammer.");
    }

    
    if (candle.IsSpinningTop()) {
        Print("The candle is a Spinning Top.");
    } else {
        Print("The candle is not a Spinning Top.");
    }
}

Now lets take an example of how you would code it without using a class

double BodySize(double open, double close) {
    return MathAbs(close - open);
}


double UpperShadowSize(double high, double open, double close) {
    return high - MathMax(open, close);
}


double LowerShadowSize(double low, double open, double close) {
    return MathMin(open, close) - low;
}


bool IsHammer(double open, double close, double high, double low) {
    double bodySize = BodySize(open, close);
    double lowerShadow = LowerShadowSize(low, open, close);
    double upperShadow = UpperShadowSize(high, open, close);

    if (bodySize == 0)
        return false;

    
    if (lowerShadow >= 2 * bodySize && upperShadow 0.1) {
        return true;
    }

    return false;
}


bool IsSpinningTop(double open, double close, double high, double low) {
    double bodySize = BodySize(open, close);
    double totalLength = high - low;
    double upperShadow = UpperShadowSize(high, open, close);
    double lowerShadow = LowerShadowSize(low, open, close);

    if (bodySize == 0 || totalLength == 0)
        return false;

    
    if (bodySize 0.3 && upperShadow >= bodySize * 0.5 && lowerShadow >= bodySize * 0.5) {
        return true;
    }

    return false;
}


void OnStart() {
    
    double openPrice = 1.1050;
    double closePrice = 1.1060;
    double highPrice = 1.1080;
    double lowPrice = 1.1040;

    
    if (IsHammer(openPrice, closePrice, highPrice, lowPrice)) {
        Print("The candle is a Hammer.");
    } else {
        Print("The candle is not a Hammer.");
    }

    
    if (IsSpinningTop(openPrice, closePrice, highPrice, lowPrice)) {
        Print("The candle is a Spinning Top.");
    } else {
        Print("The candle is not a Spinning Top.");
    }
}

Now you got to know about why you should class and why you should not?

I do not use class on my projects, I love using functions and struct only

Comment down for what reason you will use the class or if you avoid using the class like me?