Question

从我的Xcode 4.5.2编译器获取一条消息：

Property 'name' not found for object of type 'Checklist'

在DataModel.m中的这行代码：

Checklist.name = @"List";

问题是属性声明是在Checklist.h中进行的，已经导入到DataModel.m中。那么为什么会发生这种错误？

Checklist.m

#import <Foundation/Foundation.h>

@interface ChecklistItem : NSObject <NSCoding>

@property (nonatomic, copy) NSString *text;
@property (nonatomic, assign) BOOL checked;

- (void) toggleChecked;

@end

这是DataModel.m文件：

#import "DataModel.h"
#import "Checklist.h"

@implementation DataModel


- (NSString *)documentsDirectory
{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return documentsDirectory;
}

- (NSString *)dataFilePath
{
    return [[self documentsDirectory] stringByAppendingPathComponent:@"Checklists.plist"];
}

- (void)saveChecklists
{
    NSMutableData *data = [[NSMutableData alloc] init];
    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
    [archiver encodeObject:self.lists forKey:@"Checklists"];
    [archiver finishEncoding];
    [data writeToFile:[self dataFilePath] atomically:YES];
}

- (void)loadChecklists
{
    NSString *path = [self dataFilePath];
    if ([[NSFileManager defaultManager] fileExistsAtPath:path])
    {
        NSData *data = [[NSData alloc] initWithContentsOfFile:path];
        NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
        self.lists = [unarchiver decodeObjectForKey:@"Checklists"];
        [unarchiver finishDecoding];
    }
    else
    {
        self.lists = [[NSMutableArray alloc] initWithCapacity:20];
    }
}

- (void)registerDefaults
{
    NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:
                                [NSNumber numberWithInt:-1], @"ChecklistIndex",
                                [NSNumber numberWithBool:YES], @"FirstTime",
                                nil];

    [[NSUserDefaults standardUserDefaults]registerDefaults:dictionary];
}

- (void)handleFirstTime
{
    BOOL firstTime = [[NSUserDefaults standardUserDefaults] boolForKey:@"FirstTime"];
    if(firstTime) {
        Checklist *checklist = [[Checklist alloc] init];
        Checklist.name = @"List"; // error message appears here
        [self.lists addObject:checklist];
        [self setIndexOfSelectedChecklist:0];
        [[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"FirstTime"];

    }
}

- (id)init
{
    if((self = [super init])) {
        [self loadChecklists];
        [self registerDefaults];
        [self handleFirstTime];
    }
    return self;
}

- (int)indexOfSelectedChecklist
{
    return [[NSUserDefaults standardUserDefaults]integerForKey:@"ChecklistIndex"];
}

- (void)setIndexOfSelectedChecklist
{
    [[NSUserDefaults standardUserDefaults]setInteger:index forKey:@"ChecklistIndex"]; 
}

@end

Checklist.h（更正）

#import <Foundation/Foundation.h>

@interface Checklist : NSObject<NSCoding>

@property (nonatomic, copy) NSString *name;
@property (nonatomic, strong) NSMutableArray *items;

@end

Answer 1

Checklist *checklist = [[Checklist alloc] init];

在这里，您可以创建班级Checklist的对象，并将其分配给变量checklist。

Checklist.name = @"List"; // error message appears here

在这里，您使用Checklist（类）代替checklist（实例）。

该行应为

checklist.name = @"List"; // error message goes away!

DataModel.m无法查看名称的属性声明：为什么？

1 个答案: