if statement

FROM : Nathan
DATE : Tue May 27 23:24:42 2008

I'm having a weird problem.... here's my code:

- (IBAction)operators:(id)sender {
   OB=[operatorBar floatValue];
   if (OB=1) {
       [operator setFloatValue: 4];
   }
   if (OB=2) {
       [operator setFloatValue: 5];
   }
}

So you would expect that if operatorBar = 1, then OB will = 1, and 
operator will = 4. I know the first part is ok due to testing, but 
what happens when I run the program is that it acts like the if's 
don't exist, so upon using operators method operator will equal 5 no 
matter what. What's wrong here?