decodeBoolForKey

decodeBoolForKey is a method of the NSCoder class used in Apple’s Cocoa and Cocoa Touch frameworks to retrieve a boolean value that was previously encoded with a matching key. It is commonly employed when implementing the NSCoding protocol to support object serialization and deserialization.

Usage context and behavior:

Users typically implement encoding and decoding methods in a class that conforms to NSCoding. During encoding, a boolean property is stored with encodeBool:forKey:. During decoding, decodeBoolForKey: retrieves the value for the same key. If the key does not exist in the archive, the method returns NO (false). If the stored value is not a boolean, behavior may depend on the framework version and runtime checks, so consistency between encode and decode is important.

Language variations:

In Objective-C, the method is called decodeBoolForKey:. In Swift, the equivalent is decodeBool(forKey:) on NSCoder or NSKeyedUnarchiver, depending on context. The returned type is a Bool in Swift or a BOOL in Objective-C.

Example (Objective-C):

- (void)encodeWithCoder:(NSCoder *)coder {

[coder encodeBool:YES forKey:@"isEnabled"];

}

- (instancetype)initWithCoder:(NSCoder *)coder {

if (self = [super init]) {

_isEnabled = [coder decodeBoolForKey:@"isEnabled"];

}

return self;

}

Example (Swift):

required init?(coder aDecoder: NSCoder) {

isEnabled = aDecoder.decodeBool(forKey: "isEnabled")

super.init()

}

See also:

encodeBool:forKey:, decodeObjectForKey:, NSCoding, NSSecureCoding.