Plist: what it is and how to use it

Question

What exactly is a .plist file and how would I use it? When I view this in xcode, it seems to generate some kind of template vs showing me some xml code. Is there a way that I can extract the data in a plist file by pushing the contents into an array? Also, where can I view the source of the .plist?

Answer 1

You can easily get the contents of a plist into an array by using the following code (we're opening here the file called 'file.plist' that's part of the Xcode project):

NSString *filePath = [[NSBundle mainBundle] pathForResource:@"file" ofType:@"plist"];
contentArray = [NSArray arrayWithContentsOfFile:filePath];

A plist is just a XML file which corresponds to some DTD (datatype dictionary) designed by Apple, the DTD can be seen here:

http://www.apple.com/DTDs/PropertyList-1.0.dtd

The DTD -among other things- describes the "objects" and datatypes that the XML file can contain.

Answer 2

Plist is short for property list. It is just a filetype used by Apple to store data.

You can get more info here:

http://developer.apple.com/library/mac/#documentation/Darwin/Reference/ManPages/man5/plist.5.html

If you want to read in plists check here:

// Get the location of the plist
// NSBundle represents the main application bundle (.app) so this is a shortcut
// to avoid hardcoding paths
// "Data" is the name of the plist
NSString *path = [[NSBundle mainBundle] pathForResource:@"Data" ofType:@"plist"];

// NSData is just a buffer with the binary data
NSData *plistData = [NSData dataWithContentsOfFile:path];

// Error object that will be populated if there was a parsing error
NSString *error;

// Property list format (see below)
NSPropertyListFormat format;

id plist;

plist = [NSPropertyListSerialization propertyListFromData:plistData
                                mutabilityOption:NSPropertyListImmutable
                                format:&format
                                errorDescription:&error];

plist could be whatever the top level container in the plist was. For example, if the plist was a dictionary then plist would be an NSDictionary. If the plist was an array it would be an NSArray

Here the format enum:

enum {
   NSPropertyListOpenStepFormat = kCFPropertyListOpenStepFormat,
   NSPropertyListXMLFormat_v1_0 = kCFPropertyListXMLFormat_v1_0,
   NSPropertyListBinaryFormat_v1_0 = kCFPropertyListBinaryFormat_v1_0
}; NSPropertyListFormat;

http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/PropertyLists/SerializePlist/SerializePlist.html.html