关于一个简单的学生列表app的问题

Question

tableVIew数据通信app

Answer 1

首先，你的delegate要用weak或者assign，用strong会导致循环引用。currentStudent的问题，最好把StudentDetailsVIewController这个类贴出来看一下。

Answer 2

这是.h文件里的：#import <UIKit/UIKit.h>
#import "Student.h"@class StudentDetailsViewController;@protocol StudentDetailsViewControllerDelegate <NSObject>- (void)studentDetailsViewControllerDidFinish:(StudentDetailsViewController *)sender;@end@interface StudentDetailsViewController : UIViewController<UITextFieldDelegate>@property (strong, nonatomic) Student *currentStudent;@property (weak, nonatomic) IBOutlet UITextField *classNameTextField;
@property (weak, nonatomic) IBOutlet UITextField *nameTextField;
@property (weak, nonatomic) IBOutlet UITextField *numberTextField;@property (weak, nonatomic) id<StudentDetailsViewControllerDelegate>delegate;- (IBAction)revert:(id)sender;
@end这是.m文件里的：#import "StudentDetailsViewController.h"@interface StudentDetailsViewController ()@end@implementation StudentDetailsViewController- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.    
}- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
- (IBAction)revert:(id)sender {
    [self populateViewWithStudent:self.currentStudent];
}
// Populate the data
- (void)populateViewWithStudent:(Student *)student
{
    self.currentStudent = student;
    
    self.classNameTextField.text = student.className;
    self.nameTextField.text = student.name;
    self.numberTextField.text = student.number;
}- (void)viewWillAppear:(BOOL)animated
{
    [self populateViewWithStudent:self.currentStudent];
}- (void)viewWillDisappear:(BOOL)animated
{
    [self.view.window endEditing:YES];
    
    self.currentStudent.name = self.nameTextField.text;
    self.currentStudent.className = self.classNameTextField.text;
    self.currentStudent.number = self.numberTextField.text;
    [self.delegate studentDetailsViewControllerDidFinish:self];
}

Answer 3

应该是你没有传值给currentStudent属性，需要把StudentListTableViewController相关代码贴出来

Answer 4

你是用的Storyboard吗？我在你的didSelect方法里面没看到pushViewController，如果你是用的Storyboard，要在prepareForSegue里面处理，就像这样：-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(UITableViewCell *)cell{
    ViewController *destVC = (ViewController *)segue.destinationViewController;
    destVC.currentStudent = chosenStudent;
}

Answer 5

如下图，把strong改成retain

Answer 6

还有你的代理应该是assign的
@property (nonatomic, assign) id <StudentDetailsViewControllerDelegate> delegate;

Answer 7

把哪个属性的strong改成retain？

Answer 8

把哪个属性的strong改成retain？
ARC环境下，strong ＝ retain

Answer 9

我用的是storyboard用你的方法我终于成功解决了问题，但是我之前照着书上做书上的例子，并没有用prepareForSegue，而是像我之前的那样，也成功了