iOS程式設計——NSUserDefaults來儲存自定義Object

在開發過程中，經常遇到要将一些變量儲存到NSUserDefaults裡，它預設是隻支援基本對象的比如NSString、NSData等；如果儲存自定義對象，就需要實作<NSCoding>協定，來實作它的兩個方法：序列化和反序列化：

先去看下NSCoding協定的API：

@protocol NSCoding

- (void)encodeWithCoder:(NSCoder *)aCoder;
- (id)initWithCoder:(NSCoder *)aDecoder; // NS_DESIGNATED_INITIALIZER

@end
           

很簡單：隻需要實作這兩個方法就可以了，再來看看NSCoder的使用：

@interface NSCoder : NSObject

- (void)encodeValueOfObjCType:(const char *)type at:(const void *)addr;
- (void)encodeDataObject:(NSData *)data;
- (void)decodeValueOfObjCType:(const char *)type at:(void *)data;
- (NSData *)decodeDataObject;
- (NSInteger)versionForClassName:(NSString *)className;

@end
           

它的擴充：

- (void)encodeObject:(id)objv forKey:(NSString *)key;
- (void)encodeConditionalObject:(id)objv forKey:(NSString *)key;
- (void)encodeBool:(BOOL)boolv forKey:(NSString *)key;
- (void)encodeInt:(int)intv forKey:(NSString *)key;
- (void)encodeInt32:(int32_t)intv forKey:(NSString *)key;
- (void)encodeInt64:(int64_t)intv forKey:(NSString *)key;
- (void)encodeFloat:(float)realv forKey:(NSString *)key;
- (void)encodeDouble:(double)realv forKey:(NSString *)key;
- (void)encodeBytes:(const uint8_t *)bytesp length:(NSUInteger)lenv forKey:(NSString *)key;
           

- (BOOL)containsValueForKey:(NSString *)key;
- (id)decodeObjectForKey:(NSString *)key;
- (BOOL)decodeBoolForKey:(NSString *)key;
- (int)decodeIntForKey:(NSString *)key;
- (int32_t)decodeInt32ForKey:(NSString *)key;
- (int64_t)decodeInt64ForKey:(NSString *)key;
- (float)decodeFloatForKey:(NSString *)key;
- (double)decodeDoubleForKey:(NSString *)key;
- (const uint8_t *)decodeBytesForKey:(NSString *)key returnedLength:(NSUInteger *)lengthp NS_RETURNS_INNER_POINTER;   // returned bytes immutable!

- (void)encodeInteger:(NSInteger)intv forKey:(NSString *)key NS_AVAILABLE(10_5, 2_0);
- (NSInteger)decodeIntegerForKey:(NSString *)key NS_AVAILABLE(10_5, 2_0);
           

很簡單：序列化就是encodexxxx，反序列化就是deCodexxxx，讓我們來試驗下：

我們來寫一個一本書的Model:BookModel，先來看.h聲明：

#import <Foundation/Foundation.h>

typedef NS_ENUM(NSUInteger, BookType) {
    BookType_Default = 0,
    BookType_Math
};

@interface BookModel : NSObject

@property (nonatomic, assign) BookType      type;

@property (nonatomic, copy) NSString        *name;

@property (nonatomic, copy) NSString        *publisher;

@property (nonatomic, assign) BOOL          isSale;

@end
           

它聲明了四個變量，包含三種類型：枚舉類型、BOOL類型、NSString類型

下面用.m檔案對其實作序列化和反序列化：

#import "BookModel.h"

@implementation BookModel

- (instancetype) init {
    if (self == [super init]) {
        //default setting
        self.type = BookType_Default;
        self.name = nil;
        self.publisher = nil;
        self.isSale = NO;
    }
    return self;
}

- (void) encodeWithCoder:(NSCoder *)aCoder {
    [aCoder encodeInteger:self.type forKey:@"type"];
    [aCoder encodeObject:self.name forKey:@"name"];
    [aCoder encodeObject:self.publisher forKey:@"publisher"];
    [aCoder encodeBool:self.isSale forKey:@"isSale"];
}


- (id) initWithCoder:(NSCoder *)aDecoder {
    if (self == [super init]) {
        self.type = [aDecoder decodeIntegerForKey:@"type"];
        self.name = [aDecoder decodeObjectForKey:@"name"];
        self.publisher = [aDecoder decodeObjectForKey:@"publisher"];
        self.isSale = [aDecoder decodeBoolForKey:@"isSale"];
    }
    return self;
}


@end
           

OK，初始化以後就可以儲存到NSUserDefalut裡面了。