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
第一次运行它的示例屏幕截图:
连续运行的示例屏幕截图: