Question

我是Objective-C编程的新手，我正在尝试将一个新的字典对象写入一个包含字典数组的plist，以持久保存数据。

我的plist结构是：

<plist>
    <array>
        <dict>
            <key>toyName</key>
            <string>N64</string>
            <key>toyBrand</key>
            <string>Nintendo</string>
        </dict>
    </array>
</plist>

我尝试编写新字典的功能：

-(void)saveData {
    NSFileManager *fm = [NSFileManager new];
    NSError *err = nil;
    NSURL *docsurl = [fm URLForDirectory:NSDocumentDirectory
                            inDomain:NSUserDomainMask
                   appropriateForURL:nil
                              create:YES
                               error:&err];
    NSURL *url = [docsurl URLByAppendingPathComponent:@"Toy.plist"];

    NSMutableArray *plistData = [NSMutableArray arrayWithContentsOfURL:url];

    NSMutableDictionary *newDict = [[NSMutableDictionary alloc]init];

    NSDate * now = [NSDate date];

    [newDict setValue:itemText.text forKey:@"toyName"];
    [newDict setValue:brandText.text forKey:@"toyBrand"];

    [plistData addObject:newDict];
}

调用saveData函数时，使用NSLog打印时plistData数组仍然相同，并且plist并未更改。如何将新的字典对象写入包含字典数组的plist？

Answer 1

在[plistData writeToURL:url atomically:YES]下有[plistData addObject:newDict]的代码，但是必须确保plistData不是nil，而是通过url查找相应的文件。

例如：

-(void)saveData {
        NSFileManager *fm = [NSFileManager new];
        NSError *err = nil;
        NSURL *docsurl = [fm URLForDirectory:NSDocumentDirectory
                                inDomain:NSUserDomainMask
                       appropriateForURL:nil
                                  create:YES
                                   error:&err];
        NSURL *url = [docsurl URLByAppendingPathComponent:@"Toy.plist"];

        NSMutableArray *plistData = [NSMutableArray arrayWithContentsOfURL:url];

        NSMutableDictionary *newDict = [[NSMutableDictionary alloc]init];

        NSDate * now = [NSDate date];

        [newDict setValue:itemText.text forKey:@"toyName"];
        [newDict setValue:brandText.text forKey:@"toyBrand"];

        [plistData addObject:newDict];
    }

如何将新字典对象写入包含字典数组的plist

1 个答案: