NSCoding

在IOS的开发中，小数据量的持久化都用NSUserDefaults来实现，但是NSUserDefaults只能保存NSString, NSNumber, NSDate, NSArray, NSDictionary这些数据类型，但大多时候，我们会将一个对象实体做持久化的保存，由于不是大批量的数据，不会用到sqlite，那么这个时候NSUserDefaults会是很好的选择，其实对象类型可以通过NSCoding的委托方法来实现的。

1. View Code //
2. //  UserEntity.m
3. //  NSCodingDemo
4. //
5. //  Created by   on 11-5-20.
6. //  Copyright 2011  , Inc. All rights reserved.
7. //
8. #import "UserEntity.h"
9. #import "AddressEntity.h"
10. #define SAMPLEDATA_KEY_USERNAME (@"userName")
11. #define SAMPLEDATA_KEY_GENDER (@"gender")
12. #define SAMPLEDATA_KEY_AGE (@"age")
13. #define k_FRIENDS (@"frinds")
14. #define k_ADDRESS (@"address")
15. #define k_userEntity_addresses (@"addresses")
16. @implementation UserEntity
17. @synthesize userName = _userName;
18. @synthesize gender   = _gender;
19. @synthesize age      = _age;
20. @synthesize friends  = _friends;
21. @synthesize address  = _address;
22. @synthesize addresses = _addresses;
23. -(void)dealloc
24. {
25. [self.userName release];
26. [self.friends release];
27. [self.address release];
28. [self.addresses release];
29. [super dealloc];
30. }
31. - (void)encodeWithCoder:(NSCoder*)coder
32. {
33. [coder encodeObject:self.userName forKey:SAMPLEDATA_KEY_USERNAME];
34. [coder encodeInt:self.age forKey:SAMPLEDATA_KEY_AGE];
35. [coder encodeBool:self.gender forKey:SAMPLEDATA_KEY_GENDER];
36. [coder encodeObject:self.friends forKey:k_FRIENDS];
37. [coder encodeObject:self.address forKey:k_ADDRESS];
38. [coder encodeObject:self.addresses forKey:k_userEntity_addresses];
39. }
40. - (id)initWithCoder:(NSCoder*)decoder
41. {
42. if (self = [super init])
43. {
44. if (decoder == nil)
45. {
46. return self;
47. }
48. self.userName = [decoder decodeObjectForKey:SAMPLEDATA_KEY_USERNAME];
49. self.gender = [decoder decodeBoolForKey:SAMPLEDATA_KEY_GENDER];
50. self.age = [decoder decodeIntForKey:SAMPLEDATA_KEY_AGE];
51. self.friends = [decoder decodeObjectForKey:k_FRIENDS];
52. self.address = [decoder decodeObjectForKey:k_ADDRESS];
53. self.addresses = [decoder decodeObjectForKey: k_userEntity_addresses];
54. }
55. return self;
56. }
57. @end

1. View Code //
2. //  AddressEntity.m
3. //  NSCodingDemo
4. //
5. //  Created by   on 11-5-20.
6. //  Copyright 2011  , Inc. All rights reserved.
7. //
8. #import "AddressEntity.h"
9. #define k_Id (@"id")
10. #define k_AddresEntity_address (@"addrss")
11. @implementation AddressEntity
12. @synthesize Id, address;
13. -(void)dealloc
14. {
15. [self.address release];
16. [super dealloc];
17. }
18. - (NSString *)description
19. {
20. return [NSString stringWithFormat:@"id :%d address: %@" , self.Id, self.address];
21. }
22. - (void)encodeWithCoder:(NSCoder*)coder
23. {
24. [coder encodeObject:self.address forKey:k_AddresEntity_address];
25. [coder encodeInt:self.Id forKey:k_Id];
26. }
27. - (id)initWithCoder:(NSCoder*)decoder
28. {
29. if (self = [super init])
30. {
31. if (decoder == nil)
32. {
33. return self;
34. }
35. self.address = [decoder decodeObjectForKey:k_AddresEntity_address];
36. self.Id = [decoder decodeIntForKey:k_Id];
37. }
38. return self;
39. }
40. @end

1. View Code -(IBAction)write:(id)sender
2. {
3. //get document path
4. NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
5. NSString *documentsDirectory = [paths objectAtIndex:0];
6. NSString *filePath = [documentsDirectory stringByAppendingPathComponent:k_FILE_NAME];
7. NSMutableData *data = [[[NSMutableData alloc] init] autorelease];
8. NSKeyedArchiver *archiver = [[[NSKeyedArchiver alloc] initForWritingWithMutableData:data] autorelease];
9. UserEntity *userEntity = [[[UserEntity alloc] init] autorelease];
10. userEntity.age = 18;
11. userEntity.gender = NO;
12. userEntity.userName = @"add";
13. NSArray *friends = [[NSArray alloc] initWithObjects:@"ac", @"2", @"3", @"4", nil];
14. userEntity.friends = friends;
15. AddressEntity *address = [[[AddressEntity alloc] init] autorelease];
16. address.Id = 1;
17. address.address = @"china";
18. userEntity.address = address;
19. AddressEntity *address2 = [[[AddressEntity alloc] init] autorelease];
20. address2.Id = 2;
21. address2.address = @"china2";
22. AddressEntity *address3 = [[[AddressEntity alloc] init] autorelease];
23. address3.Id = 3;
24. address3.address = @"china3";
25. NSArray *addresses = [[NSArray alloc] initWithObjects:address2, address3 , nil];
26. userEntity.addresses = addresses;
27. [archiver encodeObject:userEntity forKey:@"KEY"];
28. [archiver finishEncoding];
29. BOOL success = [data writeToFile:filePath atomically:YES];
30. }
31. -(IBAction)read:(id)sender
32. {
33. NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
34. NSString *documentsDirectory = [paths objectAtIndex:0];
35. NSString *filePath = [documentsDirectory stringByAppendingPathComponent:k_FILE_NAME];
36. NSData *data = [[NSData alloc] initWithContentsOfFile:filePath];
37. NSKeyedUnarchiver *unArchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
38. UserEntity *userEntity = [unArchiver decodeObjectForKey:@"KEY"];
39. NSLog(@"name is %@ , friend %@ address :%@ , addresses is :%@", userEntity.userName , userEntity.friends , userEntity.address, userEntity.addresses);
40. }