MQL5 ReferenceLanguage BasicsData TypesString Type

String Type

The string type is used for storing text strings. A text string is a sequence of characters in the Unicode format with the final zero at the end of it. A string constant can be assigned to a string variable. A string constant is a sequence of Unicode characters enclosed in double quotes: "This is a string constant".

If you need to include a double quote (") into a string, the backslash character (\) must be put before it. Any special character constants can be written in a string, if the backslash character (\) is typed before them.

Examples:

string svar="This is a character string";
string svar2=StringSubstr(svar,0,4);
Print("Copyright symbol\t\x00A9");
FileWrite(handle,"This string contains a new line symbols \n");
string MT5path="C:\\Program Files\\MetaTrader 5";

To make the source code readable, long constant strings can be split into parts without addition operation. During compilation, these parts will be combined into one long string:

//--- Declare a long constant string
   string HTML_head="<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\""
                    " \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\">\n"
                    "<html xmlns=\"http://www.w3.org/1999/xhtml\">\n"
                    "<head>\n"
                    "<meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\" />\n"
                    "<title>Trade Operations Report</title>\n"
                    "</head>";
//--- Output the constant string into log
   Print(HTML_head);
  }

Built-in string type methods

Strings can be handled by string functions, conversion functions and built-in methods of string type provided in the table:

String method	Analog	Description
Constructor string(const int len)		Constructs a string of a specified
string[] length both for reading and writing. The index should be within BufferSize()		Provides access to the string element by a specified index
static string string.Init(const int len, const ushort character);	StringInit	Initializes a string using specified symbols with a specified size
void string.Fill(const ushort character);	StringFill	Fills in the string with a specified symbol
int string.Len();	StringLen	Returns the number of characters in a string
int string.BufferSize();	StringBufferLen	Returns the size of a buffer distributed for a string
bool string.SetLen(const int new_len);	StringSetLength	Sets a specified length (in characters) for a string
bool string.Reserve(const int buffer_len);	StringReserve	Reserves the buffer of a specified size for a string in memory
bool string.Add(const string substring);	StringAdd	Adds a specified substring to the end
int string.Concatenate(const scalar val1, const scalar val2...);	StringConcatenate	Forms a string consisting of passed parameters
array string.Split(const ushort separator, const bool long_separator);	StringSplit	Returns a string array by a specified separator
int string.Compare(const string str, const bool case_sensivity);	StringCompare	Compares with a specified string and returns 1 if the first string exceeds the second one; 0 - if the strings are equal; -1 (minus one) - if the first string is less than the second one
string string.Substr(const int start_pos, const int len);	StringSubstr	Retrieves a substring from a specified position
int string.Find(const string substr, const int pos);	StringFind	Returns an index of the position the necessary substring starts from
void string.ToLower();	StringToLower	Converts all characters to lower case
void string.ToUpper();	StringToUpper	Converts all characters to upper case
int string.TrimLeft();	StringTrimLeft	Deletes spaces, as well as carriage movement and tabulation characters to the left
int string.TrimRight()	StringTrimRight	Deletes spaces, as well as carriage movement and tabulation characters to the right
void string.Double(const double var, const int digits=8);	DoubleToString	Converts a string to a double type number
void string.Enum(const enum value);	EnumToString	Converts the enumeration value of any type into a string
void string.Integer(const int value, const int str_len=0, const ushort fill=' ');	IntegerToString	Converts a string to a long type number
void string.CharArray(const uchar array[], const int start_pos=0, const int len=-1, const uint cp=CP_ACP);	CharArrayToString	Converts part of the uchar type array to a string
void string.ShortArray(const ushort array[], const int start_pos=0, const int len=-1);	ShortArrayToString	Copies part of the ushort type array to a string
void string.Time(const datetime dt,const int mode=TIME_DATE\|TIME_MINUTES);	TimeToString	Converts datetime to the "yyyy.mm.dd hh:mi" format string.
void string.Format(const string format_str);	StringFormat	Formats the obtained parameters into a string