Should I use NSUserDefaults or a plist to store da

Question

I will be storing a few strings (maybe 10-20). I am not sure if I should use NSUserDefaults to save them, or write them out to a plist. What is considered best practice? NSUserDefaults seems like it is less lines of code, therefore quicker to implement.

I'd like to add that these string values will be added/removed by the user.

Answer 1

Using a plist is a good choice for storing your strings if the strings are not just user settings that can go in NSUserDefaults. As was mentioned, when using a plist you must store your plist in the Documents directory in order to write to it, because you can't write into your own app's resources. When I first learned this, I wasn't clear on where your own app's Bundle directory was vs. where the Documents directory was, so I thought I'd post example code here that first copies a plist called "Strings.plist" (that you already have in your own app's Bundle directory) to the Documents directory, and then writes to it and reads from it.

// Make a path to the plist in the Documents directory
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *stringsPlistPathIndDoc = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"Strings.plist"];

// Make a path to the plist in your app's Bundle directory
NSString *stringsPlistPathInBundle = [[NSBundle mainBundle] pathForResource:@"Strings" ofType:@".plist"];

NSFileManager *fileManager = [NSFileManager defaultManager];

// Check first that you haven't already copied this plist to the Documents directory
if (![fileManager fileExistsAtPath:stringsPlistPathIndDoc])
{
    NSError *error;

    // Copy the plist from the Bundle directory to the Documents directory 
    [fileManager copyItemAtPath:stringsPlistPathInBundle toPath:stringsPlistPathIndDoc error:&error];
}

// Write your array out to the plist in the Documents directory
NSMutableArray *stringsArray = [[NSMutableArray alloc] initWithObjects:@"string1", @"string2", @"string3", nil]; 
[stringsArray writeToFile:stringsPlistPathIndDoc atomically:YES];

// Later if you want to read it:
stringsArray = [[NSMutableArray alloc] initWithContentsOfFile:stringsPlistPathIndDoc];

Answer 2

The recommended way to persist data like this is to use Core Data. While NSUserDefaults can be used to store more or less anything it's only supposed to be used to store preferences.

Answer 3

NSUserDefaults will store the user preferences into a file into the Library/Preferences folder. In theory it serves only to store some application/user properties.

Plist file are usefull to manage a single file. If you need to manage more you should use the Coredata. There is no restriction about the size of the plist file. Otherwise you have to be careful with plist file because when you need to save or read it the entire contents of the file will be load into memory.

Answer 4

Using .plist

1. Create a plist using Xcode

Write a value to plist

NSURL *plistURL = [[NSBundle mainBundle] URLForResource:@"settings" withExtension:@"plist"];

 NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithContentsOfURL:plistURL];
 [dict setValue:@"value" forKey:@"key"];
 [dict writeToURL:plistURL atomically:YES];

Read a value from plist

NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithContentsOfURL:plistURL];
NSString *myValue = [dict valueForKey:@"key"];

Answer 5

I am assuming an array, but it will work with dictionaries too.

Userdefaults, Core Data and Plists can all be read/write but if you use a plist you need to pay attention in what dir you put it. See the plist part down below.

Core Data I think it's way too much overkill, it's just strings. It's supposed to be used when you want to persist more complex objects.

NSUserDefaults:

It's pretty fast and easy to do, though it's supposed to store only user settings. To write them to the userdefaults:

NSArray *stringsArray = [[NSArray alloc] arrayWithObjects: string1, string2, string3, nil];
[[NSUserDefaults standardUserDefaults] setObject:stringsArray forKey:@"MyStrings"];
[[NSUserDefaults standardUserDefaults] synchronize];

To read the from the userdefaults:

NSArray *stringsArray = [[NSUserDefaults standardUserDefaults] objectForKey:@"MyStrings"];

Plist:

If your strings are going to be modified you will need to write and read a plist but you cant't write into your app's resources.

1. To have a read/write plist first find the documents directory

   NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
   NSString *stringsPlistPath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"Strings.plist"];
   

2. Create the array (I am assuming the strings are string1, ...)

   NSArray *stringsArray = [[NSArray alloc] arrayWithObjects: string1, string2, string3, nil];
   

3. Write it to file

   [stringsArray writeToFile:stringsPlistPath atomically:YES];
   

To read the plist:

1. Find the documents directory

   NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
   NSString *stringsPlistPath = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"Strings.plist"];
   

2. Read it in:

   NSArray *stringsArray = [NSArray arrayWithContentsOfFile:stringsPlistPath];
   

Answer 6

iOS ultimately stores all NSUserDefaults data to a plist file. So it will not affect the performance if that is your concern. I personally prefer using NSUserDefaults for small data and plist for a relatively large set of data.

Note: Never store any sensitive information in NSUserDefaults as anyone can see that data.