How should text fields look like to be read by FileReadArray

[Ziad El]

For some reason I am not able to use the FileReadArray function:

1. How should fields be separated? TAB? space? semicolon? I used TABs

2. How should datetime be entered? I used D'01.01.2004' format

I copied and run the following code from MQL tutorials:

//+------------------------------------------------------------------+
//|                                      Test_Text_FileReadArray.mq5 |
//|                        Copyright 2018, MetaQuotes Software Corp. |
//|                                             https://www.mql5.com |
//+------------------------------------------------------------------+
#property copyright "Copyright 2018, MetaQuotes Software Corp."
#property link      "https://www.mql5.com"
#property version   "1.00"
//--- display the window of input parameters when launching the script
#property script_show_inputs
//--- input parameters
input string InpFileName="data.bin";
input string InpDirectoryName="SomeFolder";
//+------------------------------------------------------------------+
//| Structure for storing price data                                 |
//+------------------------------------------------------------------+
struct prices
  {
   datetime          date; // date
   double            bid;  // bid price
   double            ask;  // ask price
  };
//+------------------------------------------------------------------+
//| Script program start function                                    |
//+------------------------------------------------------------------+
void OnStart()
  {
//--- structure array
   prices arr[];
//--- file path
   string path=InpDirectoryName+"//"+InpFileName;
//--- open the file
   ResetLastError();
   int file_handle=FileOpen(path,FILE_READ|FILE_BIN);
   if(file_handle!=INVALID_HANDLE)
     {
      //--- read all data from the file to the array
      FileReadArray(file_handle,arr);
      //--- receive the array size
      int size=ArraySize(arr);
      //--- print data from the array
      for(int i=0;i<size;i++)
         Print("Date = ",arr[i].date," Bid = ",arr[i].bid," Ask = ",arr[i].ask);
      Print("Total data = ",size);
      //--- close the file
      FileClose(file_handle);
     }
   else
      Print("File open failed, error ",GetLastError());
  }

My Data bin file and results are as follows:

Please help, as I cannot find any resource on the internet giving a full example and complete explanation about this topic

[kypa]

Try writing an array, see what comes out.

https://www.mql5.com/en/docs/files/filewritearray

[Ziad El]

Tried my best:

//--- display the window of input parameters when launching the script
#property script_show_inputs

//--- input parameters
input string InpFileName="data.bin";
input string InpDirectoryName="SomeFolder";

//+------------------------------------------------------------------+
//| Structure for storing price data                                 |
//+------------------------------------------------------------------+
struct prices
  {
   double            bid;  // bid price
   double            ask;  // ask price
  };
//--- global variables
int    count=0;
int    size=20;
string path=InpDirectoryName+"//"+InpFileName;
prices arr[];
//+------------------------------------------------------------------+
//| Script program start function                                    |
//+------------------------------------------------------------------+
void OnStart()
{
  
//--- allocate memory for the array
   ArrayResize(arr,size); 
   
for (count=0; count<size ;count++)
{
   arr[count].bid=22;
   arr[count].ask=223;
}

//--- open the file
   ResetLastError();
   int handle=FileOpen(path,FILE_READ|FILE_WRITE|FILE_BIN);
   if(handle!=INVALID_HANDLE)
     {
      //--- write array data to the end of the file
      FileSeek(handle,0,SEEK_END);
      FileWriteArray(handle,arr);
      //--- close the file
      FileClose(handle);
     }
   else
      Print("Failed to open the file, error ",GetLastError());
  }

And the result is:

[Lorentzos Roussos]

Welcome 

You cannot save structures with strings in them , and you cannot read strings with structures from files .

If you reopen the second file you created (the alien scribes one) and load the second structure you created with file read array
you will notice (after printing) it reads the correctly.

[Ziad El]

Ahh! Thank you Lorentzos. Yes it reads them correctly!

[Lorentzos Roussos]

Now if you have files with strings and need to turn them to structure : 
(even though , it will be slow with big files due to the constant resizing)

input string FileName="data.bin";//File Name
input string Folder="";//File Folder
input string Delimeter=" ";//Separator
--------------------------------------
  //Data and desired structure
    struct exportdata
    {
    datetime time;
    double ask;
    double bid;
    };
    exportdata EXP[];
    int EXP_Total=0;
  //Data and desired structure ends here 
  //Open text file 
    string location=FileName;
    string raw_line_feed;
    //Line splitter prep
      ushort u_sep;                  // The code of the separator character
      string result[];               // An array to get strings
      //--- Get the separator code
      u_sep=StringGetCharacter(Delimeter,0);
    //Line splitter prep ends here 
    if(Folder!="") location=Folder+"\\"+location;
    int fop=FileOpen(location,FILE_READ|FILE_TXT);
    while(!FileIsEnding(fop))
    {
    raw_line_feed=FileReadString(fop);
    int split=StringSplit(raw_line_feed,u_sep,result);
       //increase
       if(split==3)
       {
       EXP_Total++;
       ArrayResize(EXP,EXP_Total,0);
       EXP[EXP_Total-1].time=StringToTime(result[0]);
       EXP[EXP_Total-1].ask=StringToDouble(result[1]);
       EXP[EXP_Total-1].bid=StringToDouble(result[2]);
       Print("["+IntegerToString(EXP_Total)+"] Time :"+TimeToString(EXP[EXP_Total-1].time,TIME_DATE)+" A:"+DoubleToString(EXP[EXP_Total-1].ask,2)+" B:"+DoubleToString(EXP[EXP_Total-1].bid,2));
       }
       //increase ends here 
    }
    FileClose(fop);

[William Roeder]

Ziad El:

For some reason I am not able to use the FileReadArray function: 1. How should fields be separated? TAB? space? semicolon? I used TABs

Please help, as I cannot find any resource on the internet giving a full example and complete explanation about this topic

Perhaps you should read the manual. Separated is a text file not binary.

Reads from a file of BIN type arrays of any type except string (may be an array of structures, not containing strings, and dynamic arrays).
          File Functions / FileReadArray - Reference on algorithmic/automated trading language for MetaTrader 5