Does EnumToString work with my custom defined enums in MQL5?

Yes. EnumToString works with both built-in MetaTrader enums (such as ENUM_ORDER_TYPE, ENUM_TIMEFRAMES) and user-defined enums created with the enum keyword, outputting the exact identifier name as a string.

How do I fix the warning "implicit conversion from number to string"?

Replace direct string assignments like string s = 100; with explicit conversion calls: string s = IntegerToString(100); or string s = DoubleToString(price, _Digits);.

What is the fastest way to concatenate strings in MQL5 loops?

For high-frequency loops, use StringAdd(target, source) or pre-allocate a string buffer with StringInit(). Avoid repeated string1 + string2 concatenations in tight loops as each addition allocates a temporary memory buffer.

How do I check if a string exceeds the maximum order comment length?

MetaTrader 5 broker order comments are restricted to 31 characters. Use StringLen(comment) <= 31 or truncate using StringSubstr(comment, 0, 31) before placing orders.

Can StringToDouble handle decimal commas like "1,0850"?

No. MQL5 expects standard period decimal separators ("."). If parsing external CSV feeds with commas, use StringReplace(str, ",", ".") before calling StringToDouble().

Complete MQL5 guide & code

MQL5 String Conversion Guide: EnumToString, Number Conversions & Formatting

Master MQL5 string conversion and formatting. Convert enums with EnumToString, numbers with IntegerToString and DoubleToString, concatenate strings with StringFormat, and eliminate compiler conversion warnings.

Generate custom MQL5 code with AI View the MQL5 code

What this MQL5 guide covers

EnumToString converts any native or custom enum value into its readable code identifier string.

Avoid implicit number-to-string conversions which trigger compiler warnings and cause precision truncations.

Use DoubleToString(val, digits) with explicit symbol digits to avoid trailing floating-point inaccuracies.

StringFormat provides clean printf-style string formatting for order comments, chart overlays, and log outputs.

Essential MQL5 Type-to-String Conversion Functions

MQL5 is a strongly typed C++-like language. While MQL4 frequently allowed silent implicit conversions, MQL5 enforces explicit conversions to prevent algorithmic trading calculation bugs.

The standard library provides purpose-built conversion functions for enums, integers, and floating-point doubles.

Conversion Function	Input Type	Return Type	Example Output
EnumToString(val)	Enumeration enum	string	EnumToString(POSITION_TYPE_BUY) -> "POSITION_TYPE_BUY"
IntegerToString(val, len, fill)	long / int / ulong	string	IntegerToString(105, 5, '0') -> "00105"
DoubleToString(val, digits)	double	string	DoubleToString(1.08456, 4) -> "1.0846"
StringToDouble(str)	const string	double	StringToDouble("1.0850") -> 1.085000
StringToInteger(str)	const string	long	StringToInteger("100234") -> 100234
StringLen(str)	const string	int	StringLen("Pineify") -> 7

String Concatenation: Plus Operator vs StringFormat

MQL5 offers multiple approaches to combine strings. For simple phrases, the + operator suffices. For complex diagnostic logs with mixed numbers, prices, and timestamps, StringFormat is vastly superior in readability and execution efficiency.

Plus operator (+): string msg = "Ticket: " + IntegerToString(ticket);
StringFormat: string msg = StringFormat("Ticket: %I64u, Price: %.*f", ticket, digits, price);
StringAdd: In-place string appending without allocating temporary string buffers in loops.

Resolving Implicit Conversion Compiler Warnings

In MetaEditor, assigning a numeric variable directly to a string variable triggers warning: "implicit conversion from number to string".

In financial systems, implicit double conversions can round prices unexpectedly. Always wrap numeric variables in IntegerToString() or DoubleToString(val, _Digits) to make your intent explicit to the compiler.

Implementation details & mechanics

Core implementation pattern

When formulating order comments or logging trade execution, always format strings explicitly: use StringFormat("Magic_%I64u_v%s", InpMagicNumber, InpVersion) to construct safe, non-truncated comments that stay within the broker’s 31-character comment limit.

Error handling & safety rules

When logging position closures or error events, convert ENUM_TRADE_RETCODE and ENUM_POSITION_TYPE using EnumToString(). This outputs clear, searchable log entries in the MT5 Experts tab rather than opaque numeric codes.

MQL5 Code Implementation Code

//+------------------------------------------------------------------+
//|                                       StringConversionGuide.mq5 |
//|                             Copyright 2026, Pineify Guides Series |
//|                                              https://pineify.app |
//+------------------------------------------------------------------+
#property copyright "Pineify Guides Series"
#property link      "https://pineify.app/mql5/string-conversion-guide"
#property version   "1.00"
#property script_show_inputs

// Example custom enum
enum ENUM_STRATEGY_REGIME
  {
   REGIME_TREND_FOLLOWING = 1, // Trend Following
   REGIME_MEAN_REVERSION  = 2, // Mean Reversion
   REGIME_BREAKOUT        = 3  // Volatility Breakout
  };

input ENUM_STRATEGY_REGIME InpRegime = REGIME_TREND_FOLLOWING;

//+------------------------------------------------------------------+
//| Script program start function                                    |
//+------------------------------------------------------------------+
void OnStart()
  {
   Print("--- 1. Enum to String Conversion ---");
   // Convert built-in MQL5 enums
   ENUM_POSITION_TYPE posType = POSITION_TYPE_BUY;
   ENUM_TIMEFRAMES tf = PERIOD_H1;
   Print("Built-in Position Type: ", EnumToString(posType));
   Print("Built-in Timeframe:     ", EnumToString(tf));

   // Convert custom user-defined enum
   Print("User Defined Strategy:  ", EnumToString(InpRegime));

   Print("--- 2. Numbers to String Conversion ---");
   // Integer to String with zero-padding
   ulong orderTicket = 8945201;
   string ticketStr = IntegerToString(orderTicket);
   string paddedTicket = IntegerToString(orderTicket, 10, '0');
   Print("Ticket String: ", ticketStr, " | Padded: ", paddedTicket);

   // Double to String with exact decimal precision
   double rawPrice = 1.0845672;
   int digits = (int)SymbolInfoInteger(_Symbol, SYMBOL_DIGITS);
   string priceStr = DoubleToString(rawPrice, digits);
   PrintFormat("Raw double: %.7f -> DoubleToString with %d digits: %s",
               rawPrice, digits, priceStr);

   Print("--- 3. String to Numbers (Parsing) ---");
   string inputPriceStr = "2745.80";
   string inputLotsStr  = "150";

   double parsedPrice = StringToDouble(inputPriceStr);
   long parsedLots    = StringToInteger(inputLotsStr);
   PrintFormat("Parsed double: %.2f | Parsed integer: %I64d",
               parsedPrice, parsedLots);

   Print("--- 4. String Length and Concatenation ---");
   string baseText = "Pineify MQL5 Code Generator";
   int textLen = StringLen(baseText);
   PrintFormat("String: '%s' (Length: %d chars)", baseText, textLen);

   // Formatting complex string with StringFormat (printf style)
   string orderComment = StringFormat("%s | #%I64u | %.2f lots | %s",
                                      _Symbol,
                                      orderTicket,
                                      0.25,
                                      EnumToString(InpRegime));
   Print("Formatted Order Comment: ", orderComment);
  }

Copy this code into MetaEditor, save it in your MQL5 folder (Experts, Scripts, or Include), and compile with F7.

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Frequently Asked Questions

Related MQL5 pages

Datetime Guide→Fileopen Csv Guide→Ctrade Class Guide→Magic Number Guide→

Technical references

Risk and testing note

Past performance is not indicative of future results. Backtest statistics are based on historical data and do not guarantee future profits. Trading involves significant risk of loss. This content is for educational purposes only and does not constitute financial advice.