NSUserDefaults保存或传递数据

-(void)viewDidLoad{
    //NSUserDefault可以保存数据到内存中，通过-(BOOL) synchronize可以保存到IOS设备的存储器中
    //创建NSUserDefaults
    NSUserDefaults *userDef = [NSUserDefaults standardUserDefaults];
    //保存NSString
    [userDef setObject: @"test1" forKey:"tt"]; 
    //保存UIImage
    UIImage *image = [UIImage imageNamed:@"tupian.png"];
    //转换为NSData对象
    NSData *imageData = UIImageJPEGRepresentation(image, 1);
    //UIImageJPEGRepresentation(第一个参数是UIImage对象，第二个参数是表示最大压缩比例)1表示不压缩，0表示最大压缩。
    [userDef setObject:imageData forKey:@"image"];
}
//方法如下：
-(void)setFloat:(float)forKey:(NSString *)defaultName;
-(void)setBool:(BOOL)forKey:(NSString *)defaultName;
-(void)setInteger:(NSInteger)forKey:(NSString *)defaultName;
-(void)setObject:(id)forKey:(NSString *)defaultName;
-(void)setDouble:(double)forKey:(NSString *)defaultName;
-(void)setURL:(NSURL *)forKey:(NSString *)defaultName;
//其中setObject中的id只支持
//NSData NSString NSNumber NSArray NSDictionary;NSArray 和NSDictionary 中也只能包含这几种类型
-(void)viewDidLoad{
    //获取
    NSUserDefaults *userDef = [NSUserDefaults standardUserDefaults];
    NSString *string = [userDef stringForKey: @"tt"];
    NSData *data = [userDef dataForKey:@"image"];
    UIImage *image = [UIImage imageWithData:data];
}
//所有获取的方法如下：
-(NSInteger)integerForKey:(NSString *)defaultName;
-(BOOL)boolForKey:(NSString *)defaultName;
-(float)floatForKey:(NSString *)defaultName;
-(double)doubleForKey:(NSString *)defaultName;
-(NSData *)dataForKey:(NSString *)defaultName;
-(NSArray *)stringArrayForKey:(NSString *)defaultName;
-(NSURL *)URLForKey:(NSString *)defaultName;
-(NSString *)stringForKey:(NSString *)defaultName;
-(NSDictionary *)dictionaryForKey:(NSString *)defaultName;
-(id)objectForKey:(NSString *)defaultName;
-(NSArray *)arrayForKey:(NSString *)defaultName;