CODEWITHSUNDEEP
objective-cnsdictionarynsmutabledictionary
Alwaysblue
Alwaysblue

Reputation: 11830

BOOL value changing from NO to Yes when setting up from NSDictionary

I have this code

if ([args valueForKey:@"showSetupScreen"]) {
    BOOL showSetupScreen = [args valueForKey:@"showSetupScreen"];
    NSLog(showSetupScreen ? @"YES" : @"NO");
    //  meetingConfig.showSetupScreen = showSetupScreen;
}

Where args is NSMutableDictionary.

args value in my dictionary is NO but when I set to BOOL showSetupScreen = [args valueForKey:@"showSetupScreen"]; it changes into YES

Can someone help me in comprehending why this could be happening.

Attached Screenshot for your reference

enter image description here

Upvotes: 0

Views: 335

Answers (2)

Artem
Artem

Reputation: 413

[args valueForKey:@"showSetupScreen"] statement returns pointer (address in memory) and it has two options: some address (non zero value) and NULL (zero). For C programming language true is any non zero value (any address in memory in our case). And for this reason you get true in if operator and in showSetupScreen variable. But it only tells you that there is some object in the dictionary for the specified key, but not the value of this key (the value wrapped in this object). To get this value (BOOL in our case), you must call the boolValue.

Upvotes: 0

Rob
Rob

Reputation: 437452

A NSDictionary (or NSMutableDictionary) cannot directly contain a primitive C type, such as BOOL. Primitive numeric types (including Boolean) in NSDictionary are wrapped in NSNumber objects. See Numbers Are Represented by Instances of the NSNumber Class and Most Collections Are Objects.

Thus, use NSNumber method boolValue to extract the Boolean from the NSNumber, e.g.,

BOOL showSetupScreen = [[args valueForKey:@"showSetupScreen"] boolValue];

Or, more simply:

BOOL showSetupScreen = [args[@"showSetupScreen"] boolValue];

E.g., examples with primitive C types, including BOOL, NSInteger, and double:

NSDictionary *args = @{
    @"foo": @NO,
    @"bar": @YES,
    @"baz": @42,
    @"qux": @3.14
};

BOOL foo = [args[@"foo"] boolValue];         // NO/false
BOOL bar = [args[@"bar"] boolValue];         // YES/true
NSInteger baz = [args[@"baz"] integerValue]; // 42
double qux = [args[@"qux"] doubleValue];     // 3.14

For what it's worth, if you expand the values contained within args, that will show you the internal types for those values, and you will see that that the value associated with showSetupScreen (or foo in my example), is not a BOOL, but rather a pointer to a __NSCFBoolean/NSNumber:

enter image description here

Upvotes: 3

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