Dictionary's and plist files

Question

Hi all,

I have written some code that pulls info from a plist file and does a couple of things then eventually pops this data into a table.

This all works fine, the problem is I wrote the code pulling the data from a plist file within the resources folder, but the actual file will be created via an action and stored in memory. I need some help on getting my code working when pulling it from the new location.

current working code:

- (void) loadData{
// Load items
NSString *error;
NSPropertyListFormat format;
NSString *path = [[NSBundle mainBundle] pathForResource:@"CalculatorData" ofType:@"plist"];
NSData *plistData = [NSData dataWithContentsOfFile:path];
NSArray *amountData = [NSPropertyListSerialization propertyListFromData:plistData mutabilityOption:NSPropertyListImmutable format:&format errorDescription:&error];
NSDictionary *amountData = [NSPropertyListSerialization propertyListFromData:plistData mutabilityOption:NSPropertyListImmutable format:&format errorDescription:&error];

if (amountData) {
    self.amounts = [[NSMutableArray alloc] initWithCapacity:[amountData count]];
    result = 0;
    for (NSDictionary *amountsDictionary in amountData) {

        [self.amounts addObject:amountsDictionary];

        currentNumber = [[amountsDictionary objectForKey:@"Value"] floatValue];

        if ([[amountsDictionary objectForKey:@"Type"] isEqualToString:@"Plus"]) {
            result = result + currentNumber;
        } else {
            result = result - currentNumber;
        }
    }
    //Set main amount
    NSString *msg = [NSString stringWithFormat:@"£%.2f",result];
    [lblAmount setText:msg];
} else {
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:nil message:@"Why not keep track of your income and expensies? Add new items below." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alert show];
    [alert release];
}
}

I think to pull the info from the new file location i need something similar to below, but can't seem to get the output the same as above:

//Get file location
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *path = [documentsDirectory stringByAppendingPathComponent:@"saveBudget.plist"];

// read it back in with different dictionary variable
NSMutableDictionary *amountData = [NSMutableDictionary dictionaryWithContentsOfFile:path];
if(amountData==nil ){
    NSLog(@"failed to retrieve dictionary from disk");
} else {  
    NSLog(@"%@", amountData);
}

The code creating the plist file is (this also needs a little work, as its currently always overwriting what was done before, when I would like it to add a new array):

-(void) addData {

// create a dictionary to store a fruit's characteristics
NSMutableDictionary *items = [[NSMutableDictionary alloc] init];
[items setObject:@"10" forKey:@"Value"];
[items setObject:@"tester" forKey:@"Description"];
[items setObject:@"Plus" forKey:@"Type"];

// create a dictionary to store all fruits
NSMutableDictionary *plist = [[NSMutableDictionary alloc] init];
[plist setObject:items forKey:@"0"];

//Get file location
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *path = [documentsDirectory stringByAppendingPathComponent:@"saveBudget.plist"];

// write plist to disk
[plist writeToFile:path atomically:YES];
}

This also needs a little work as I would like it to be:

    <?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"&gt;
<plist version="1.0">
<array>
    <dict>
        <key>Date</key>
        <string>27/9/10</string>
        <key>Value</key>
        <string>10.97</string>
        <key>Description</key>
        <string>PaperRound</string>
        <key>Type</key>
        <string>Plus</string>
    </dict>
    <dict>
        <key>Date</key>
        <string>27/9/10</string>
        <key>Value</key>
        <string>10.97</string>
        <key>Description</key>
        <string>PaperRound</string>
        <key>Type</key>
        <string>Plus</string>
    </dict>
    <dict>
        <key>Date</key>
        <string>27/9/10</string>
        <key>Value</key>
        <string>10.97</string>
        <key>Description</key>
        <string>PaperRound</string>
        <key>Type</key>
        <string>Plus</string>
    </dict>
    <dict>
        <key>Date</key>
        <string>27/9/10</string>
        <key>Value</key>
        <string>10.97</string>
        <key>Description</key>
        <string>PaperRound</string>
        <key>Type</key>
        <string>Plus</string>
    </dict>
</array>
</plist>

Sorry for the long post but hopefully should be everything that relates. Any help on this would be great.

Answer 1

If you want the outermost element of the plist to be an array, then the following lines in the code you posted are creating an object of the wrong type:

// create a dictionary to store all fruits
NSMutableDictionary *plist = [[NSMutableDictionary alloc] init];
[plist setObject:items forKey:@"0"];

I would also beware of leaving stale comment statements in your code, as they can sometimes cause you to mislead yourself. Here's a suggested rewrite of your addData method:

-(void)addData {

    // Create a dictionary representing an item
    //
    NSDictionary *item = [NSDictionary dictionaryWithObjectsAndKeys:
                          @"10", @"Value",
                          @"tester", @"Description",
                          @"Plus", @"Type",
                          nil];

    // Create an array of items. This must be an instance of NSArray or
    // NSMutableArray if you want the corresponding element in your plist
    // to be an array.
    //
    NSArray *items = [NSArray arrayWithObjects: item, nil];

    // Get file location (this part is fine).
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *path = [documentsDirectory stringByAppendingPathComponent:@"saveBudget.plist"];

    // Write array of items to filesystem
    [items writeToFile:path atomically:YES];
}

With apologies, I haven't tested the above code, but it should at least serve to illustrate the point.