Question

Imagine that you are reading json data from the server continuously. let’s say, you are getting weather data. I want to show only data 2 hours back from now. Whenever user clicks on the play button, it would show weather data on the map.
How I could save json data first then show it on the map. Because that would enhance my application instead of connecting server , getting data and showing it at the same time. please just give me advice. Do I need to save it first as a plist or an array? Where should I keep this data before I simulate?

Answer 1

Storing it in the plist in the documents directory is a good way of saving data for later reference.If you want to save the JSON string you can also opt for NSUSerDefaults..(preferably if the string is not too large)

Saving to plist..

 NSURL  *url = [NSURL URLWithString:serverPath];
    NSData *urlData = [NSData dataWithContentsOfURL:url];
    if ( urlData )
    {
        NSArray       *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

        NSString  *documentsDirectory = [paths objectAtIndex:0];  

        NSString  *filePath = [NSString stringWithFormat:@"%@/myplist.plist", documentsDirectory];

        [urlData writeToFile:filePath atomically:YES];
    }

and retrieving it..

NSArray *paths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);

NSString *documentsDirectory = [paths objectAtIndex:0];

NSString  *filePath = [documentsDirectory stringByAppendingPathComponent: 
                      [NSString stringWithFormat: @"%@/myplist.plist",documentsDirectory ] ];

NSData *retrievedData   = [NSData dataWithContentsOfFile:filePath];