xCode iOS未注册：
currentCard = [myBook getCard:cardIndex];
在一个字符串中调用get方法（名称）时遇到一些困难 对象（addressCard）在一个特定的索引（int index）中 NSMutableArray（book），在一个对象（addressBook）中。
基本上，iOS viewController有自己的addressBook实例，它在实例化的NSMutableArray中保存addressCards。但是在viewController的viewLoad中，AddressBook却没有获得该卡。
在这种特殊情况下，是否有一些特定的语法形式？
相当新的iOS，因为它的应用程序有几个文件，但主要问题与addressBook.m的addCard和getCard方法直接相关。项目基于Kochan学习Objective-C的课程，如果有人熟悉它（或者可以推荐更好的iOS学习源）。
Method within AddressBook.m
//Add a method for getting the current card in view
-(AddressCard*) getCard: (int) index{
AddressCard *cardC = [book objectAtIndex:index];
return cardC;
}
ViewController.m
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
{
BOOL isNew;
int cardIndex;
AddressBook *myBook;
AddressCard *currentCard;
BOOL cardChanged;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
//Initialize the Address Book
NSString *presetName1 = @"Dave Strider";
NSString *presetName2 = @"Rose Tyler";
NSString *presetName3 = @"Sherlock Holmes";
NSString *presetEmail1 = @"TurntechGodhead@skaia.net";
NSString *presetEmail2 = @"DoctorsBetterHalf@tardis.Who";
NSString *presetEmail3 = @"SHolmes@221Baker.st";
AddressCard *card1 = [[AddressCard alloc]init];
AddressCard *card2 = [[AddressCard alloc]init];
AddressCard *card3 = [[AddressCard alloc]init];
[card1 setName: presetName1 andEmail:presetEmail1];
[card2 setName: presetName2 andEmail:presetEmail2];
[card3 setName: presetName3 andEmail:presetEmail3];
[myBook addCard:card1];
[myBook addCard:card2];
[myBook addCard:card3];
//set the addybook index to zero
cardIndex = 0;
//set card to current card
//***** ISSUE IS HERE *****
currentCard = [myBook getCard:cardIndex];
//set field values ***** currentCard gains no variables.
[_nameField setText:[currentCard name]];
[_emailField setText:[currentCard email]];
isNew = false;
cardChanged = false;
//***** TESTING SYNTAX *****
// This method however works perfectly, the card, and its string are accepted ****
// [_nameField setText:[card1 name]];
// [_nameField setText:presetName1];
// [_emailField setText:presetEmail1];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)btnNext_touch:(id)sender {
//check bools
//go to next card, check for last.
int i = [myBook entries];
if (i == cardIndex)
{cardIndex = 0;}
else {
cardIndex++;
}
//reset current bools
isNew = false;
cardChanged = false;
//set card to current card
currentCard = [myBook getCard:cardIndex];
//set field values
[_nameField setText:[currentCard name]];
[_emailField setText:[currentCard email]];
}
- (IBAction)nameFieldChanged:(id)sender {
cardChanged = true;
// if (isNew != true)
// {
// [_nameField setText:[];
//} else{
//}
}
- (IBAction)emailFieldChanged:(id)sender {
cardChanged = true;
}
@end
如果他们在理解这个小问题时提供额外的帮助，那么这是其他类。
ViewController.h
//
// ViewController.h
// Lozano007-p4
//
// Created by antonio a lozano ii on 2/19/13.
// Copyright (c) 2013 antonio a lozano ii. All rights reserved.
//
#import <UIKit/UIKit.h>
#import "AddressBook.h"
@interface ViewController : UIViewController
@property (strong, nonatomic) IBOutlet UITextField *nameField;
@property (strong, nonatomic) IBOutlet UITextField *emailField;
@property (strong, nonatomic) IBOutlet UIButton *btnNext;
- (IBAction)btnNext_touch:(id)sender;
- (IBAction)nameFieldChanged:(id)sender;
- (IBAction)emailFieldChanged:(id)sender;
@end
AddressCard.h
//
// AddressCard.h
// Lozano007-p4
//
// Created by antonio a lozano ii on 2/19/13.
// Copyright (c) 2013 antonio a lozano ii. All rights reserved.
//
#import <Foundation/Foundation.h>
@interface AddressCard : NSObject <NSCopying, NSCoding>
@property (nonatomic, copy) NSString *name, *email;
-(void) setName: (NSString *) theName andEmail: (NSString *) theEmail;
-(void) assignName: (NSString *) theName andEmail: (NSString *) theEmail;
-(NSComparisonResult) compareNames: (id) element;
-(void) print;
@end
AddressCard.m
//
// AddressCard.m
// Lozano007-p4
//
// Created by antonio a lozano ii on 2/19/13.
// Copyright (c) 2013 antonio a lozano ii. All rights reserved.
//
#import "AddressCard.h"
@implementation AddressCard
@synthesize name, email;
-(void) setName: (NSString *) theName andEmail: (NSString *) theEmail
{
self.name = theName;
self.email = theEmail;
}
// Compare the two names from the specified address cards
-(NSComparisonResult) compareNames: (id) element
{
return [name compare: [element name]];
}
-(void) print
{
NSLog (@"====================================");
NSLog (@"| |");
NSLog (@"| %-31s |", [name UTF8String]);
NSLog (@"| %-31s |", [email UTF8String]);
NSLog (@"| |");
NSLog (@"| |");
NSLog (@"| |");
NSLog (@"| O O |");
NSLog (@"====================================");
}
-(id) copyWithZone: (NSZone *) zone
{
id newCard = [[[self class] allocWithZone: zone]init];
[newCard assignName: name andEmail: email];
return newCard;
}
-(void) assignName: (NSString *) theName andEmail: (NSString *) theEmail
{
name = theName;
email = theEmail;
}
-(void) encodeWithCoder: (NSCoder *) encoder
{
[encoder encodeObject: name forKey: @"AddressCardName"];
[encoder encodeObject: email forKey: @"AddressCardEmail"];
}
-(id) initWithCoder: (NSCoder *) decoder
{
name = [decoder decodeObjectForKey: @"AddressCardName"];
email = [decoder decodeObjectForKey: @"AddressCardEmail"];
return self;
}
@end
AddressBook.h
//
// AddressBook.h
// Lozano007-p4
//
// Created by antonio a lozano ii on 2/19/13.
// Copyright (c) 2013 antonio a lozano ii. All rights reserved.
//
#import <Foundation/Foundation.h>
#import "AddressCard.h"
@interface AddressBook: NSObject <NSCopying, NSCoding>
//{
//Add a mutable array for the address cards
// NSMutableArray *cardArray;
//}
@property (nonatomic, copy) NSString *bookName;
@property (nonatomic, strong) NSMutableArray *book;
-(id) initWithName: (NSString *) name;
-(void) sort;
-(void) addCard: (AddressCard *) theCard;
-(void) sort2;
-(void) removeCard: (AddressCard *) theCard;
-(int) entries;
-(void) list;
-(AddressCard *) lookup: (NSString *) theName;
//Add a getMethod for the Current Display'd card.
-(AddressCard*) getCard: (int) index;
@end
AddressBook.m
//
// AddressBook.m
// Lozano007-p4
//
// Created by antonio a lozano ii on 2/19/13.
// Copyright (c) 2013 antonio a lozano ii. All rights reserved.
//
#import "AddressBook.h"
@implementation AddressBook
@synthesize book, bookName;
// set up the AddressBook's name and an empty book
-(id) initWithName: (NSString *) name
{
self = [super init];
if (self) {
bookName = [NSString stringWithString: name];
book = [NSMutableArray array];
}
return self;
}
-(id) init
{
return [self initWithName: @"Unnamed Book"];
}
// Write our own book setter to create a mutable copy
-(void) setBook: (NSArray *) theBook
{
book = [theBook mutableCopy];
}
-(void) sort
{
[book sortUsingSelector: @selector(compareNames:)];
}
// Alternate sort using blocks
-(void) sort2
{
[book sortUsingComparator:
^(id obj1, id obj2) {
return [[obj1 name] compare: [obj2 name]];}];
}
-(void) addCard: (AddressCard *) theCard
{
[book addObject: theCard];
}
-(void) removeCard: (AddressCard *) theCard
{
[book removeObjectIdenticalTo: theCard];
}
-(int) entries
{
return [book count];
}
-(void) list
{
NSLog (@"======== Contents of: %@ =========", bookName);
for ( AddressCard *theCard in book )
NSLog (@"%-20s %-32s", [theCard.name UTF8String],
[theCard.email UTF8String]);
NSLog (@"==================================================");
}
// lookup address card by name — assumes an exact match
-(AddressCard *) lookup: (NSString *) theName
{
for ( AddressCard *nextCard in book )
if ( [[nextCard name] caseInsensitiveCompare: theName]
== NSOrderedSame )
return nextCard;
return nil;
}
-(void) encodeWithCoder: (NSCoder *) encoder
{
[encoder encodeObject:bookName forKey: @"AddressBookBookName"];
[encoder encodeObject:book forKey: @"AddressBookBook"];
}
-(id) initWithCoder: (NSCoder *) decoder
{
bookName = [decoder decodeObjectForKey: @"AddressBookBookName"];
book = [decoder decodeObjectForKey: @"AddressBookBook"];
return self;
}
// Method for NSCopying protocol
-(id) copyWithZone: (NSZone *) zone
{
id newBook = [[[self class] allocWithZone: zone] init];
[newBook setBookName: bookName];
// The following will do a shallow copy of the address book
[newBook setBook: book];
return newBook;
}
//Add a method for getting the current card in view
-(AddressCard*) getCard: (int) index{
AddressCard *cardC = [book objectAtIndex:index];
return cardC;
}
@end
- 再一次，没有专门用代码生成错误消息。更重要的是，顶部指定的代码行对代码没有任何影响。
答案 0 :(得分：0)
这是ViewController的全部来源吗？如果是这样，我看不到您创建地址簿实例的位置。
一般情况下，如果您发送消息并且没有任何反应，则应检查“某事”是否为零。在你的Java时代，你会看到一个NPE。在这种语言中，没有任何反应。 'myBook'可能在这里没有。
viewDidLoad中应该这样做：
myBook = [[AddressBook alloc] initWithName:@"Some Name"];