CODEWITHSUNDEEP
objective-carraysabifunction-call
ilya n.
ilya n.

Reputation: 18816

[NSArray arrayWithObjects: nil, nil]

I have a property self.shareURL that may or may not be nil and I'd like to wrap it in array. Obviously, if it's nil I can't do that, so I'd like to have an empty array in that case. So I can write:

NSArray *items = [self shareURL] ? @[[self shareURL]] : @[];

However, I can construct it in one call to shareURL, like this:

NSArray *items = [NSArray arrayWithObjects:[self shareURL], nil];

This works because arrayWithObjects: will stop anyway once it sees the first nil and the stack is not corrupted because Objective-C ABI doesn't require it to clear the varargs in the stack.

Is it ok to use the second form? Or is the first one more clear?

Upvotes: 0

Views: 1406

Answers (4)

ilya n.
ilya n.

Reputation: 18816

Ok, for the record, I actually went with 

NSMutableArray *items = [NSMutableArray new];
if (self.shareURL) {
    [items addObject: self.shareURL];
}

as it makes more clear that there is a "default" state of empty array, and we try to add one object.

Upvotes: 0

Wei
Wei

Reputation: 3482

Both ways are OK, and the first one you can write like this:

NSArray *items = [self shareURL] ? : @[];

This is right.

NSArray *items = [self shareURL] ? @[[self shareURL]] : @[];

Upvotes: 0

Abizern
Abizern

Reputation: 150655

Rather than terseness, I would opt for readability:

NSArray *items = nil;
if ([self shareURL]) {
    items = @[[self shareURL]];
} else {
    items = @[];
}

Upvotes: 1

Antonio MG
Antonio MG

Reputation: 20410

Both options seem ok, but if you are asking for which one is more clear, I'd go for this one:

NSArray *items = [self shareURL] ? @[[self shareURL]] : @[];

Why? Because you are implementing the behaviour you want to achieve in that line, not as a consequence of something happening on the stack like on the second approach. In other words, you are achieving the behaviour you are specifying in the line.

If I'm a developer and I see that code, with the 1st approach I'll understand the behaviour, without any explanation.

Upvotes: 2

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