CODEWITHSUNDEEP
objective-cxcode
nmock
nmock

Reputation: 1907

Warning for assignment in an if statement?

Is there a way I can get a warning when I'm assigning a variable instead of checking equality? There have been many times where I have accidentally assigned, rather than compared, and it would be great to have a warning!

Is there a way Xcode can warn me without having to change coding styles to:

if (YES == aVariable) {...}

Upvotes: 3

Views: 3798

Answers (2)

yfrancis
yfrancis

Reputation: 2616

The compiler flag Wparentheses should do the trick. It will force you to place parentheses around assignments in a conditional in order to compile. Clang has this flag set by default.

Upvotes: 1

rob mayoff
rob mayoff

Reputation: 385540

Xcode already warns you if you use = instead of == in an if statement in most cases. If you're not getting the warning, tell us what version of Xcode you're using, how old your project is, and what build settings you have changed from their defaults.

My test: I created a brand new iOS app in Xcode 4.5.2 and didn't change any build settings. I just added a little code to application:didFinishLaunchingWithOptions: to trigger the warning. Here it is:

Using the result of an assignment as a condition without parentheses

You can disable the warning by setting the compiler's -Wno-parentheses flag (but why would you want to?). You can suppress the warning in a particular case by adding an extra set of parentheses around the assignment:

if ((x = 7)) {

There are two cases where you don't get the warning by default. First, in an init method, you can assign to self, like this:

- (id)init {
    if (self = [super init]) {     // no warning by default
    ...

Second, in any context, you can assign the result of the nextObject selector, like this:

while (object = [enumerator nextObject]) {    // no warning by default

You can enable warnings in these cases by setting the compiler's -Widiomatic-parentheses flag.

Upvotes: 10

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