Serialization Objective C not working - objective-c

Question

I'm trying to make an app with Objective C.
I'm trying to serialise an array existing out of objects and after wards deserialise it. Inside the object there are the methods
(id)initWithCoder:(NSCoder *)coder` and `encodeWithCoder:(NSCoder *)coder
But it seems the "rootObject" stays "nil" in the "loadDataFromDisk" -method
Here is my code :
#import "Alarm.h"
#implementation Alarm
#synthesize array = _array;
#synthesize time = _time;
#synthesize coder = _coder;
-(id)initWithCoder:(NSCoder *)coder
{
self = [super init];
if(self)
{
_array = [coder decodeObjectForKey:#"array"];
_time = [coder decodeObjectForKey:#"time"];
}
return self;
}
-(void)encodeWithCoder:(NSCoder *)coder
{
[coder encodeObject:self.array forKey:#"array"];
[coder encodeObject:self.time forKey:#"time"];
}
#end
My save and load methods :
-(void)saveDataToDisk
{
NSString * path = [self pathForDataFile];
NSLog(#"Writing alarms to '%#' %lu", path, (unsigned long)array.count);
NSMutableDictionary * rootObject;
rootObject = [NSMutableDictionary dictionary];
[rootObject setValue:array forKey:#"alarms"];
[NSKeyedArchiver archiveRootObject:rootObject toFile:path];
}
-(void)loadDataFromDisk
{
NSString *path = [self pathForDataFile];
NSDictionary *rootObject = [NSMutableDictionary dictionary];
rootObject = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
// "array" is an array with Objects of "Alarm"
array = [rootObject valueForKey:#"alarms"];
NSLog(#"Loaded from : %# %lu",path ,(unsigned long)array.count);
}
I hope anyone can help me out with this.
Thanks in advance.

Answer 1

You #synthized the array backing store (ivar) as _array. So you need to access the array as either _array or self.array. In saveDataToDisk and loadDataFromDisk it is accessed as array.
To test your array coding try something simple like this:
NSLog(#"array: %#", self.array);
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:self.array];
NSLog(#"data: %#", data);
NSArray *recovered = [NSKeyedUnarchiver unarchiveObjectWithData:data];
NSLog(#"recovered: %#", recovered);
Note: There is no need to wrap your array in a NSMutableDictionary.
When that works change it to the file based method calls.
Check that the filePath is valid.
Check that the file is created.
Check that the file contents are the same as in the above test code.
Note: There is no reason to wrap your array in a NSMutableDictionary.