Question

我试图建立一个餐厅排队应用，其第一页将有三个按钮，其中一个是“新预订”。点击它时，它会打开一个新视图，其中包含客户姓名，电话号码和总人数，服务员将输入他们订单的预计时间，然后按Enter键将所有这些值保存在plist中。我指的是youtube视频来创建plist，但是我有一个视图控制器类，我在其中初始化plist以及一个控制保存数据的NewReservation类。根据视频，我在viewDidLoad方法中创建plist，并在按钮的IBAction中复制几行，然后输入详细信息＆＃34;。我弄错了，无法访问NewReservation课程中的值，请澄清一下。谢谢。

ViewController.h

#import <UIKit/UIKit.h>
@class NewReservation;

@interface ViewController : UIViewController

@property (nonatomic , strong) NewReservation *Res;

@end

ViewController.m

 #import "ViewController.h"
#import "NewReservation.h"

@interface ViewController ()

@end

@implementation ViewController{
    NSMutableArray *phoneNumbers , *name , *noOfPeople , *estTime;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.Res = [[NewReservation alloc] init];
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsPath = [paths objectAtIndex:0];
    NSString *plistPath = [documentsPath stringByAppendingPathComponent:@"Property List.plist"];

    if(![[NSFileManager defaultManager] fileExistsAtPath:plistPath]){
        plistPath = [[NSBundle mainBundle] pathForResource:@"Property List" ofType:@"plist"];
    }
    NSData *plistXML = [[NSFileManager defaultManager] contentsAtPath:plistPath];
    NSString *errorDesc = nil;

    NSPropertyListFormat format;

    NSDictionary *temp = (NSDictionary *) [NSPropertyListSerialization propertyListWithData:plistXML options:NSPropertyListMutableContainersAndLeaves format:&format error:&errorDesc];
    if(!temp){
        NSLog(@"Error Reading plist: %@ , format: %lu",errorDesc , format);
    }
    name = [NSMutableArray arrayWithArray:[temp objectForKey:@"name"]];
    phoneNumbers = [NSMutableArray arrayWithArray:[temp objectForKey:@"phoneNumbers"]];
    noOfPeople = [NSMutableArray arrayWithArray:[temp objectForKey:@"noOfPeople"]];
    estTime    = [NSMutableArray arrayWithArray:[temp objectForKey:@"estTime"]];
    //Confused how to go further




}




- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

NewReservation.h

#import <UIKit/UIKit.h>

@interface NewReservation : UIViewController{

}
@property (weak, nonatomic) IBOutlet UITextField *name;
@property (weak, nonatomic) IBOutlet UITextField *phoneNumber;
@property (weak, nonatomic) IBOutlet UITextField *noOfPeople;
@property (weak, nonatomic) IBOutlet UITextField *estTime;
- (IBAction)nameReturn:(id)sender;

- (IBAction)enterDetails:(id)sender;



@end

NewReservation.m

#import "NewReservation.h"

@implementation NewReservation




- (IBAction)enterDetails:(id)sender{
    if([self.name.text isEqualToString:@""] || [self.phoneNumber.text isEqualToString:@""] || [self.noOfPeople.text isEqualToString:@""] || [self.estTime.text isEqualToString:@""]) {
        UIAlertView *error = [[UIAlertView alloc] initWithTitle:@"Oops" message:@"You must complete all fields!" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [error show];
    }
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsPath = [paths objectAtIndex:0];
    NSString *plistPath = [documentsPath stringByAppendingPathComponent:@"Property List.plist"];

   //Cant continue here cause its confusing me, i need to add the values and update the list everytime a new 'name,noOfPersons,phoneNumber,estTime
    //is entered.


}


@end

Answer 1

实例变量对于类是唯一的。默认情况下，只有类和子类可以访问它。因此，作为面向对象编程的基本原理，实例变量（ivars）是私有的 - 它们由类封装。

相比之下，属性是一个公共值，可能与实例变量对应也可能不对应。如果你想公开一个ivar，你可能会做一个相应的财产。但与此同时，您希望保密的实例变量没有相应的属性，因此无法从类外部访问它们。您还可以使用与ivar不对应的计算属性...

如果没有属性，可以隐藏ivars。事实上，除非在公共标题中声明ivar，否则很难确定这样的ivar存在。

您的子课程的属性与ivar不对应要使用属性访问ivar，ivar需要从子类中合成属性。

 @implementation NewReservation
 @synthesize phoneNumbers, name, noOfPeople, estTime;
 // ****
 @end

创建Plist iOS

1 个答案: