从 plist 读取，然后将对象保存到不同的 plist iOS

Posted 2023-02-23

【中文标题】从 plist 读取，然后将对象保存到不同的 plist iOS

【英文标题】：Reading from a plist and then saving objects to a different plist iOS

【发布时间】：2012-10-26 18:46:44

【问题描述】：

四处搜索后，我发现了大量关于我想做的点点滴滴的帖子，但没有一个可以一起工作。

基本上我有一个静态 plist 文件。我不想改变它的内容。 plist 文件是从 plist 读取并存储在 NSArray 中的字典数组，数据显示在表格上。这是完整且简单的部分！

我现在想做的是有一个 plist，它将用户对从静态 plist 数组读取的对象的收藏夹存储到收藏夹的 NSMutableArray 中。每当用户选择收藏夹部分时，都需要将该数组读入收藏夹表中

这个概念真的很简单，用户将按下“添加到收藏夹按钮”，字典对象将被添加到收藏夹数组中，但我的问题是正确检查收藏夹 plist 是否存在。如果是，则将该数据读入收藏夹数组。如果 is 不存在，则创建一个空的 plist，它仍然会读入收藏夹数组，但它是空的。

对于这种特殊情况，我不确定从哪里开始，有什么想法吗？非常感谢！

【参考方案1】：

我自己也遇到了这个问题，第一次尝试做同样的事情。主要问题是您不能写入不存在的 plist。因此，您需要在捆绑包中制作一个，并将其复制到您需要的位置，“如果它不存在”。这是一个例子。这不仅仅是“最小”，但我认为它解释了问题。结果是通过将某些内容存储在文档目录中某处的“data.plist”中，从而从一次运行转移到另一次运行。

在ViewController.m（例如）：

#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

第一次运行的截图示例：

连续运行的示例截图：