Data persistence for complex data

1. Custom classes to implement data persistence adhere to the <NSCopying> protocol

2. Properties in the class to do the following

The encoding protocol is to enable the object of the current class to be converted to NSData type data by a fixed encoding rule

-(void) Encodewithcoder: (Nscoder *) acoder{

[Acoder encodeObject:self.message_id forkey:@ "message_id"];

}

The decoding protocol is called when the NSData type of data is converted to an object of the current class at the time of the anti-archive. The key to decode is consistent with the key specified at the time of encoding.

-(ID) Initwithcoder: (Nscoder *) adecoder{

if (self = [super init]) {

self.message_id = [Adecoder decodeobjectforkey:@ "message_id"];

}

return self;

}

3. Save data: Achieve data archiving [Nskeyedarchiver Archiverootobject: (ID) rootobject tofile: (NSString *) path];

4. Fetch data: Reverse Archive for data [Nskeyedunarchiver unarchiveobjectwithfile: (NSString *) path];

Data persistence for complex data