I was reading about initializing the archived objects from a XIB file and found that
- (id)initWithCoder:(NSCoder *)aDecoder
is a way of doing it. But I am not able to get a hang around this. Can someone show me an simple example of how to do this?
Thanks a ton
The NSCoder class is used to archive/unarchive (marshal/unmarshal, serialize/deserialize) of objects.
This is a method to write objects on streams (like files, sockets) and being able to retrieve them later or in a different place.
I would suggest you to read Archiving
You also need to define the following method as follows:
- (void)encodeWithCoder:(NSCoder *)enCoder
{
[super encodeWithCoder:enCoder];
[enCoder encodeObject:instanceVariable forKey:INSTANCEVARIABLE_KEY];
// Similarly for the other instance variables.
....
}
And in the initWithCoder method initialize as follows:
- (id)initWithCoder:(NSCoder *)aDecoder
{
if(self = [super initWithCoder:aDecoder]) {
self.instanceVariable = [aDecoder decodeObjectForKey:INSTANCEVARIABLE_KEY];
// similarly for other instance variables
....
}
return self;
}
You can initialize the object standard way i.e
CustomObject *customObject = [[CustomObject alloc] init];
Example taken from this answer
You can use it in following way:
.h file
@interface Score : NSObject {
NSString *Username;
NSString *TotalPoints;
NSString *LifeRemains;
NSString *ScoreDate;
}
@property (nonatomic, retain) NSString *Username;
@property (nonatomic, retain) NSString *TotalPoints;
@property (nonatomic, retain) NSString *LifeRemains;
@property (nonatomic, retain) NSString *ScoreDate;
in .m file
@synthesize Username, TotalPoints, LifeRemains, ScoreDate;
- (void)encodeWithCoder:(NSCoder *)encoder
{
//Encode properties, other class variables, etc
[encoder encodeObject:self.Username forKey:kScoreUsername];
[encoder encodeObject:self.TotalPoints forKey:kScoreTotalPoints];
[encoder encodeObject:self.LifeRemains forKey:kScoreLifeRemains];
[encoder encodeObject:self.ScoreDate forKey:kScoreDate];
}
- (id)initWithCoder:(NSCoder *)decoder
{
self = [super init];
if( self != nil )
{
//decode properties, other class vars
self.Username = [decoder decodeObjectForKey:kScoreUsername];
self.TotalPoints = [decoder decodeObjectForKey:kScoreTotalPoints];
self.LifeRemains = [decoder decodeObjectForKey:kScoreLifeRemains];
self.ScoreDate = [decoder decodeObjectForKey:kScoreDate];
}
return self;
}
Happy Coding...
