从plist读取然后将对象保存到不同的plist iOS

Question

在搜索之后，我发现了大量关于我想要做的事情的点点滴滴的帖子，但没有任何可以一起工作的帖子。

Bassically我有一个静态plist文件。我不想改变它的内容。 plist文件是一个字典数组，从plist中读取并存储在NSArray中，数据显示在表中。这是一个完全有效且简单的部分！

我现在要做的是，有一个plist，它将从静态plist数组中读取的对象的用户收藏夹存储到收藏夹的NSMutableArray中。每当用户选择收藏夹部分

时，都需要将此数组读入收藏夹表中

这个概念很简单，用户会按下“添加到收藏夹”按钮＆＃34;字典对象将被添加到收藏夹数组，但我的问题是正确检查收藏夹plist是否存在。如果是，请将该数据读入收藏夹数组。如果不存在，则创建空plist，它仍将读入收藏夹数组，但它将为空。

我不知道从哪个特定情况开始，有什么想法？非常感谢！

Answer 1

在尝试第一次做同样的事情时，我自己也遇到了这个问题。主要问题是你不能写入不存在的plist。因此，您需要在捆绑中创建一个，并将其复制到您需要的位置，“如果它不存在”。这是一个例子。它比“最小”更多，但我认为它解释了这些问题。结果是通过将某些内容存储在文档目录中隐藏的“data.plist”中，从一次运行转移到另一次运行。

在ViewController.m（例如）中：

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

////////////////////////////
// BIG NOTE:
// In order for ANY of this to work, you need to make a data.plist in your supporting files, in your project,
// before compiling and running
// The plist should, at very least, have a single row with key "key1" and value "value1"
////////////////////////////

// returns path where plist file is
// "internal" means whether we want from one baked into the app (which is read-only, by the way), or one in our documents dir
-(NSString *)localPathForPlist:(NSString *)name internal:(bool)internal
{
    if( internal ) return [[NSBundle mainBundle] pathForResource:name ofType:@"plist"];
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory
               // this just adds name and ".plist" to make a filename something like "data.plist"
               stringByAppendingPathComponent:[NSString stringWithFormat:@"%@%@", name, @".plist"]
           ];
}

// write value to key, either in internal plist or not
-(void) writeToPlist:(NSString *)key setValue:(NSString *)value internal:(bool)internal
{
    NSString* path = [ self localPathForPlist:@"data" internal:internal ];
    NSMutableDictionary *plistData = [[NSMutableDictionary alloc] initWithContentsOfFile:path];
    [plistData setObject:value forKey:key];
    [plistData writeToFile:path atomically:YES];
}

// read value from key, either in internal plist or not
-(NSString *) readFromPlist:(NSString *)key internal:(bool)internal
{
    NSString* path = [ self localPathForPlist:@"data" internal:internal ];
    NSMutableDictionary *plistData = [[NSMutableDictionary alloc] initWithContentsOfFile:path];
    return (NSString *)[plistData valueForKey:key];
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    // here we go through all the different cases, trying to edit things internally and in externally,
    // and copying the internal one to the external location, towards the end, if it's not already there

    NSString *localPath    = [self localPathForPlist:@"data" internal:FALSE];
    NSString *internalPath = [self localPathForPlist:@"data" internal:TRUE];

    NSLog( @"local path=%@", localPath );

    NSFileManager *fileManager = [NSFileManager defaultManager];
    BOOL localPlistExists = [fileManager fileExistsAtPath:localPath];

    // the first time you run this, it'll do one, then the other for all other runs:
    if( localPlistExists ) NSLog( @"local plist exists" );
    else                   NSLog( @"local plist does NOT exist" );

    NSLog( @"key1's value from internal=%@", [self readFromPlist:@"key1" internal:TRUE ] );
    NSLog( @"key1's value from external=%@", [self readFromPlist:@"key1" internal:FALSE] );

    NSLog( @"setting internal key1 to new-value1" );
    [self writeToPlist:@"key1" setValue:@"new-value1" internal:TRUE ];

    NSLog( @"setting external key1 to new-value1" );
    [self writeToPlist:@"key1" setValue:@"new-value1" internal:FALSE];

    NSLog( @"key1's value from internal=%@", [self readFromPlist:@"key1" internal:TRUE ] );
    NSLog( @"key1's value from external=%@", [self readFromPlist:@"key1" internal:FALSE] );

    // the first time you run this, it'll do one, then the other for all other runs:
    if( localPlistExists ) NSLog( @"since local plist exists, leaving alone" );
    else
    {
        NSLog( @"since local plist does NOT exist, cloning from internal copy");
        [fileManager copyItemAtPath:internalPath toPath:localPath error:nil];
    }

    NSLog( @"key1's value from internal=%@", [self readFromPlist:@"key1" internal:TRUE ] );
    NSLog( @"key1's value from external=%@", [self readFromPlist:@"key1" internal:FALSE] );

    NSLog( @"setting internal key1 to new-value1" );
    [self writeToPlist:@"key1" setValue:@"new-value1" internal:TRUE ];

    NSLog( @"setting external key1 to new-value1" );
    [self writeToPlist:@"key1" setValue:@"new-value1" internal:FALSE];

    NSLog( @"key1's value from internal=%@", [self readFromPlist:@"key1" internal:TRUE ] );
    NSLog( @"key1's value from external=%@", [self readFromPlist:@"key1" internal:FALSE] );

    // notice that from one run to another, changes to the internal one don't "carry over", because it's read-only
    // but ones in the external one do
}

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

@end

第一次运行时的屏幕截图示例：

连续运行的示例屏幕截图：