"@TRUE" in Objective-C

Question

Recently I saw this code:

WKWebViewConfiguration *configuration = [[WKWebViewConfiguration alloc] init];
[configuration.preferences setValue:@TRUE forKey:@"xxxx"];

What does @TRUE stands for? I'm seeing this construct for the first time.

I know that YES equals to true and

@YES equals to NSNumber nubmerWithBool, but what does the @TRUE stands for?

StackOverflow question wtih example using "@TRUE" construct

By the way, in the answer you mention `@YES` would be a better solution. — Sulthan, Apr 29 '19 at 12:54
Of course, it's the standard. The question was about the `@TRUE` as I've seen it for the first time — Richard Topchii, Apr 29 '19 at 13:22

Sulthan · Accepted Answer · 2019-04-29T11:38:47.207

2

If you preprocess:

NSNumber *test = @TRUE;

it ends up being

NSNumber *test = @1;

(a clang literal for [NSNumber numberWithInt:1]).

which is logical, considering TRUE is preprocessed to 1.

This might be easier to see on:

#define MY_STRING "my_string"

NSString *string = @MY_STRING;

which gets preprocessed to:

NSString *string = @"my_string";

edited Apr 29 '19 at 11:38

answered Apr 29 '19 at 11:33

Sulthan

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score 1 · Answer 2 · answered Apr 29 '19 at 11:34

It's an NSNumber literal, a way of creating NSNumber instances from scalar literal expressions.

From The Clang 9 documentation:

In Objective-C, any character, numeric or boolean literal prefixed with the '@' character will evaluate to a pointer to an NSNumber object initialized with that value. C’s type suffixes may be used to control the size of numeric literals.

"@TRUE" in Objective-C

2 Answers2