iOS Unbelievable Xcode Problem -- Totally Illogical

[tod]

This is driving me insane. Here is my code exactly:

	int x;
	x=3;
	
	if (x=517) {
	[SoundServices playSoundWithName:@"switch-17" type:@"wav"];
	}

And it plays the sound every time. How could this be?

 

[sammich]

You're missing the extra "=" in the conditional.

It's actually true because the assignment of 517 to x worked.

But yeah, that kind of stuff would drive me nuts too, back in the day.

 

[SilentPanda]

Should it be x==517?

 

[tod]

Thank you. I thought == was only for strings. Shows how much I have to learn.

 

[ulbador]

You're missing the extra "=" in the conditional.

It's actually true because the assignment of 517 to x worked.

But yeah, that kind of stuff would drive me nuts too, back in the day.

Me too. Someone long ago when I first started in Borland C told me something to avoid this:

if (517 = x) {

}

I got into the habit of always putting the primitive first in comparisons such as these

 

[plinden]

Just to emphasize something here - if you find yourself blaming the SDK (whether XCode, Eclipse, Visual C++ etc) for some code not behaving the way you expect, it's 99.99999% certain to be a bug in your code.

(x = 517) always equates to true. ulbador's habit is a good one to get into.

 

[sammich]

Me too. Someone long ago when I first started in Borland C told me something to avoid this:

if (517 = x) {

}

I got into the habit of always putting the primitive first in comparisons such as these

Cool trick. I might remember that one.

As for a similar, more recent occurrence of this bug, I tried to be 'compact':

if ((some_var = do_something(blah)) < 10)

 

[ChOas]

Thank you. I thought == was only for strings. Shows how much I have to learn.

That would be isEqualToString:

 

[dejo]

That would be isEqual:

Or better yet, isEqualToString:

 

[PhoneyDeveloper]

gcc has a warning for this. It's called Missing Braces and Parentheses in the Xcode project settings.

Warn if parentheses are omitted in certain contexts, such as when there is an assignment in a context where a truth value is expected, or when operators are nested whose precedence people often get confused about.

You should probably turn on as many warnings as you can stand.

 

[ulbador]

Just to emphasize something here - if you find yourself blaming the SDK (whether XCode, Eclipse, Visual C++ etc) for some code not behaving the way you expect, it's 99.99999% certain to be a bug in your code.

(x = 517) always equates to true. ulbador's habit is a good one to get into.

Ha, that's so funny you say that. I worked with someone who constantly blamed the compiler whenever he ran into a bug where the fix wasn't immediately obvious.

"I just found a HUGE bug in Java/PHP" was his favorite line, at least once a week. Of course it wasn't like we were using development versions of Java or PHP.

Good times and laughs