Draw Canvas and Hists out of own program

ROOT
#1

Hello,

i’ve programmed a litte programm which generates random numbers and puts them into a TH1F:

#include <iostream>
#include <stdio.h>
#include "src/RandomIT.cpp"
#include <TH1F.h>
#include <TCanvas.h>
#include <TFile.h>
using namespace std;

int main (void)
{
  TFile *RootFile = new TFile("Test.root", "RECREATE");
  RandomIT *t = new RandomIT();
  TH1F *h = new TH1F("Test", "TEST", 100, 0, 1);
  for (int i = 0; i < 10000; i++)
    {
//      cout << t -> GetRandomNumber() << endl;
      h -> Fill(t -> GetRandomNumber());
    }
  TCanvas *c = new TCanvas("Test", "Test", 800, 600);
  c -> Draw();
  h -> Draw();
  RootFile -> Write();
  return 0;
}

I compile it with g++ outside of root with a little makefile:

CC=g++
SOURCES=RandomTest.cpp
OBJECTS=$(SOURCES:.cpp=.o)
CFLAGS = -c -g -Wall `root-config --cflags`
LDFLAGS = `root-config --glibs`
EXECUTABLE=RandomTest

all: $(SOURCES) $(EXECUTABLE)
    
$(EXECUTABLE): $(OBJECTS)
    $(CC) $(LDFLAGS) $(OBJECTS) -o $@

.cpp.o:
    $(CC) $(CFLAGS) $< -o $@

clean:
  rm -rf *.o $(EXECUTABLE)

The root file can be created and its possible to read it out afterwards.
But why its not possible to show the canvas and the hist?
Has someone a hint what i’am doing wrong?
Thanks in advance.

Jo

#2

Hi,

sorry for the doppelpost, but just as i posted i remembered something, i changed the program to:

#include <iostream>
#include <stdio.h>
#include "src/RandomIT.cpp"
#include <TH1F.h>
#include <TCanvas.h>
#include <TFile.h>
#include <TApplication.h>
using namespace std;

void RandomTest()
{
TFile *RootFile = new TFile("Test.root", "RECREATE");
  RandomIT *t = new RandomIT();
  TH1F *h = new TH1F("Test", "TEST", 100, 0, 1);
  for (int i = 0; i < 10000; i++)
    {
//      cout << t -> GetRandomNumber() << endl;
      h -> Fill(t -> GetRandomNumber());
    }
  TCanvas *c = new TCanvas("Test", "Test", 800, 600);
  c -> Draw();
  h -> Draw();
  RootFile -> Write();
}
int main (int argc, char **argv)
{
  TApplication theApp("App", &argc, argv);
  RandomTest();
  theApp.Run();
  return 0;
}

and it works.
Sorry again.
Jo