Question

我想使用Magical Record将2个实体（Person，Group）保存在一起。

//Model
// Person : name (Relationship : group 'To One')
// Group  : groupName (Relationship : person 'To Many')

“person.name”可以保存，但是“person.group.groupName”无法保存。

当我签入NSLog时，“person.group.groupName”为零。

“self.groupName.text”是正确的值。

应该注意，在预先注册的UIPickerView数据中选择了“self.groupName.text”。因此，不能使用[Group MR_createEntity]。

请告诉我如何解决。谢谢。

SecondViewController.h

#import <UIKit/UIKit.h>
#import "Person.h"
#import "Group.h"

@class Person, Group;

@interface SecondViewController : UIViewController

@property (nonatomic, retain) Person *person;

@end

SecondViewController.m

#import "SecondViewController.h"
#import "AppDelegate.h"
#import "Person.h"
#import "Group.h"
#import "FirstViewController.h"

@interface SecondViewController ()<UIPickerViewDelegate,UIPickerViewDataSource,UITextFieldDelegate,UINavigationControllerDelegate,NSFetchedResultsControllerDelegate>

{
    BOOL isDispGroupPicker;
    UIPickerView *picker;
    int selectedGroupRow;
}

@property (weak, nonatomic) IBOutlet UITextField *nameField;
@property (weak, nonatomic) IBOutlet UITextField *groupField;
@property (strong, nonatomic) UIView *accessoryView;
- (IBAction)saveBtn:(id)sender;

@end

@implementation SecondViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.nameField.delegate = self;
    self.groupField.delegate = self;
    isDispGroupPicker = NO;

    picker = [[UIPickerView alloc] init];
    picker.frame = CGRectMake(0, 550, 320, 180);
    picker.showsSelectionIndicator = YES;
    picker.delegate = self;
    picker.dataSource = self;
    picker.tag = 1;
    [self.view addSubview:picker];
}

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

#pragma mark - save

- (IBAction)saveBtn:(id)sender
{
    NSManagedObjectContext *context = [NSManagedObjectContext MR_defaultContext];
    Person *person = [Person MR_createEntity];
    person.name = _nameField.text;
    //person.group.groupName = _groupField.text;

    Group *group = [[self.fetchedResultsController fetchedObjects] objectAtIndex:selectedGroupRow];
    person.group.groupName = group.groupName;

    NSLog(@"%@",group.groupName);       // OK
    NSLog(@"%@",person.group.groupName);// null->NG

    [context MR_saveToPersistentStoreAndWait];
}

#pragma mark - keyboard

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
    [self.view endEditing:YES];
    return NO;
}

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField {
    BOOL ret = YES;
    if (textField == _nameField) {
        if(isDispGroupPicker) {
            [self hidePicker];
            [_accessoryView removeFromSuperview];
        }

    } else if (textField == _groupField) {
        [_nameField resignFirstResponder];
        if(!isDispGroupPicker) {
            picker.frame = CGRectMake(0, 550, 320, 216);
            [self showPicker];
            [self inputPickerClose];
            isDispGroupPicker = YES;
        }
        ret = NO;
    }
    return ret;
}

#pragma mark - FetchedResultsController

- (NSFetchedResultsController*)fetchedResultsController
{
    if(_fetchedResultsController == nil){
        self.fetchedResultsController = [Group MR_fetchAllSortedBy:@"groupName" ascending:YES withPredicate:nil groupBy:nil delegate:self];
    }
    return _fetchedResultsController;
}

#pragma mark - GroupPicker

- (void)showPicker {
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0.2];
    [UIView setAnimationDelegate:self];
    picker.frame = CGRectMake(0, 320, 320, 216);
    [UIView commitAnimations];
}

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
    return 1;
}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    return [[self.fetchedResultsController fetchedObjects] count];
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    Group *group = [[self.fetchedResultsController fetchedObjects] objectAtIndex:row];
    return group.groupName;
}

- (void) pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    Group *group = [[self.fetchedResultsController fetchedObjects] objectAtIndex:row];
    self.groupField.text = group.groupName;
    selectedGroupRow = row;
}

- (void)inputPickerClose {
    _accessoryView =[[UIView alloc] initWithFrame:CGRectMake(0,310,320,44)];
    _accessoryView.backgroundColor = [UIColor lightGrayColor];
    [self.view addSubview:_accessoryView];

    UIButton* closeButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    closeButton.frame = CGRectMake(230,10,100,27);
    [closeButton setTitle:@"Done" forState:UIControlStateNormal];
    UIButton* cancelButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    cancelButton.frame = CGRectMake(0,10,100,27);
    [cancelButton setTitle:@"Cancel" forState:UIControlStateNormal];

    [closeButton addTarget:self action:@selector(doneGroup:) forControlEvents:UIControlEventTouchUpInside];
    [cancelButton addTarget:self action:@selector(cancelGroup:) forControlEvents:UIControlEventTouchUpInside];
    [_accessoryView addSubview:closeButton];
    [_accessoryView addSubview:cancelButton];
}

- (void)doneGroup:(id)sender {
    [self hidePicker];
    [_accessoryView removeFromSuperview];
}

- (void)cancelGroup:(id)sender {
    [self hidePicker];
    [_accessoryView removeFromSuperview];
    _groupField.text = nil;
}

- (void)hidePicker {
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0.3];
    [UIView setAnimationDelegate:self];
    picker.frame = CGRectMake(0, 600, 320, 216);
    [UIView commitAnimations];
    isDispGroupPicker = NO;
}

@end

Person.h

#import <Foundation/Foundation.h>

@class Group;

@interface Person : NSManagedObject

@property (nonatomic, retain) NSString *name;
@property (nonatomic, retain) NSString *image;
@property (nonatomic, retain) Group *group;

@end

Answer 1

Picker应该选择Group（显示名称）而不是group.name，然后设置person.group = group。

-update

现在，在选择器上你选择组名并尝试将该名称附加到person.group.name，但是person.group当时是nil，所以你的代码什么都不做。因此，您的选择器必须返回一个Group对象，而不仅仅是它的名称 - 您可以将所有组加载到NSArray并从选择器位置选择它的索引。之后，您将正确选择要附加到Person对象（person.group）的Group对象。

如何使用Magical Record保存2个实体

1 个答案: