iOS文件系统中的数据归档

Question

这是我第一次将数据归档到文件系统中，我想要检查我的代码。这个简单的测试项目如预期的那样工作，但我想看看我所做的工作是否遵循了最佳实践。打开应用程序，放入文本字段，按下按钮，字符串保存并显示在标签中。当app重新打开时，保存的字符串将出现在标签中。

Cars.h

@interface Car : NSObject <NSCoding>
@property (nonatomic, copy) NSString *year;
@property (nonatomic, copy) NSString *make;
@property (nonatomic, copy) NSString *model;
@end

Cars.m

NSString *const kYearKey = @"YearKey";
NSString *const kMakeKey = @"MakeKey";
NSString *const kModelKey = @"ModelKey";

@implementation Car

-(void)encodeWithCoder:(NSCoder *)aCoder {
[aCoder encodeObject:self.year forKey:kYearKey];
[aCoder encodeObject:self.make forKey:kMakeKey];
[aCoder encodeObject:self.model forKey:kModelKey];
}
-(instancetype)initWithCoder:(NSCoder *)aDecoder {
self = [super init];
if (self != nil) {
    _year = [aDecoder decodeObjectForKey:kYearKey];
    _make = [aDecoder decodeObjectForKey:kMakeKey];
    _model = [aDecoder decodeObjectForKey:kModelKey];
}
return  self;
}
@end

ViewController.m

@interface ViewController () <UITextFieldDelegate>

@property (weak, nonatomic) IBOutlet UITextField *yearTextField;
@property (weak, nonatomic) IBOutlet UITextField *makeTextField;
@property (weak, nonatomic) IBOutlet UITextField *modelTextField;
@property (weak, nonatomic) IBOutlet UILabel *yearLabel;
@property (weak, nonatomic) IBOutlet UILabel *makeLabel;
@property (weak, nonatomic) IBOutlet UILabel *modelLabel;
@property (strong, nonatomic) NSString *yearString;
@property (strong, nonatomic) NSString *makeString;
@property (strong, nonatomic) NSString *modelString;

- (IBAction)doneButton:(id)sender;

@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.

[self loadCarInfo];
}

-(void)loadCarInfo {

NSString *path = [self archivePath];
Car *returnedCarInfo = [NSKeyedUnarchiver unarchiveObjectWithFile:path];

NSString *year = [[NSString alloc] initWithFormat:@"%@", returnedCarInfo.year];
NSString *make = [[NSString alloc] initWithFormat:@"%@", returnedCarInfo.make];
NSString *model = [[NSString alloc] initWithFormat:@"%@", returnedCarInfo.model];

_yearLabel.text = year;
_makeLabel.text = make;
_modelLabel.text = model;
}

-(BOOL)saveCarInfo {

NSString *path = [self archivePath];

Car *myCar = [[Car alloc] init];
myCar.year = _yearString;
myCar.make = _makeString;
myCar.model = _modelString;

//archive the object to the file & return YES on success
return [NSKeyedArchiver archiveRootObject:myCar toFile:path];

}

- (IBAction)doneButton:(id)sender {

_yearString = [[NSString alloc] initWithString:_yearTextField.text];
_makeString = [[NSString alloc] initWithString:_makeTextField.text];
_modelString = [[NSString alloc] initWithString:_modelTextField.text];

BOOL success = [self saveCarInfo];
if (success) {
    [self loadCarInfo];
}
}

-(NSString *)archivePath {

NSArray *documentDirectories= NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
                                                                 NSUserDomainMask, YES);
//get the document directory from that list
NSString *documentDirectory = [documentDirectories firstObject];

return [documentDirectory stringByAppendingPathComponent:@"savedText.txt"];
}


-(BOOL)textFieldShouldReturn:(UITextField *)textField {

[textField resignFirstResponder];

return YES;
}

@end

Answer 1

密码看起来没问题。我只想就两件事发表意见：

• 当您只保留对Car对象的引用时，为什么在视图控制器中保留单个字段作为属性？
• 您不需要将插座连接到所有标签，除非您计划在代码中更改它们(例如，本地化或自定义它们)