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Get value from core data property and sum it

jsantojsanto Posts: 30New Users @

i´m using the code below to get the values in one of my core data property´s, but i don´t know if it is possible to extract and them sum them, and i was wondering if someone could help me with this:

AppDelegate *appDelegate =[[UIApplication sharedApplication] delegate];
self.contextTotal=[appDelegate managedObjectContext];

NSEntityDescription *entity= [NSEntityDescription entityForName:@CellSave inManagedObjectContext:contextTotal];
NSFetchRequest *request= [[NSFetchRequest alloc] init];
[request setEntity:entity];
[request setResultType:NSDictionaryResultType];
[request setReturnsDistinctResults:YES];
[request setPropertiesToFetch:[NSArray arrayWithObject:@smtrCbrData]];
NSArray *objects= [contextTotal executeFetchRequest:request error:nil];
NSLog (@results: %@",objects);

The results are:

Structure[1595:11603] results: (
smtrCbrData = "\U20ac 770.00";
smtrCbrData = "\U20ac 3,080.00";

Is it possible to get the numbers and them sum them? how can i perform this?



  • RickSDKRickSDK Posts: 1,240Registered Users @ @ @ @
    its unclear what you are asking. "objects" is an array of NSManagedObjects. as in many objects. You can then step through them one at a time and extract values based on your schema. Your schema presumably has fields. What field are you referring to?
  • jsantojsanto Posts: 30New Users @
    Hello Rick

    Sorry for taking so long to answer and thanks for commenting. I already discovered a way to get the values from my core data properties, and i had to make some changes(change my properties to double instead of strings)...Meanwhile another problem appears but first let me show you my code:

    NSFetchRequest* request = [NSFetchRequest fetchRequestWithEntityName:@Ent];
    [request setResultType:NSDictionaryResultType];
    [request setReturnsDistinctResults:YES];
    NSExpressionDescription *expressionDescription = [[NSExpressionDescription alloc] init];
    [expressionDescription setName:@count];
    [expressionDescription setExpressionResultType:NSDoubleAttributeType];

    NSExpression *keyPathExpression = [NSExpression expressionForKeyPath:@smtrCbrData];
    NSExpression* expr = [NSExpression expressionForFunction:@sum: arguments:@[keyPathExpression]];
    [expressionDescription setExpression:expr];
    [request setPropertiesToFetch:@[@smtrCbrData,expressionDescription]];

    NSError* error = nil;
    NSArray* objects = [contextApuramento executeFetchRequest:request error:&error];

    if (objects.count >0)
    id value = [[objects valueForKey:@count]objectAtIndex:0];
    self.cobCstTl.text = [formatter stringFromNumber:[NSNumber numberWithDouble:[value doubleValue]]];
    NSLog (@results: %@",objects);

    I´m trying to sum the values from each property i have, and show the result in a specific textfield....I´m going to have multiple you can see the amount of work i´ll have....There´s got to be a BETTER! way of doing this...I´m wide open to any advice.

  • RickSDKRickSDK Posts: 1,240Registered Users @ @ @ @
    usually code might look more like this:

    NSArray* objects = [contextApuramento executeFetchRequest:request error:&error];
    int sum=0;
    for(NSManagedObject *object in objects) {
    int value = [object valueForKey:@count] intValue];
    sum += value;

    or something like that.
  • GHuebnerGHuebner Posts: 665Registered Users @ @ @
    edited June 2013
    I would watch the WWDC core data sessions online. They talk about what you want to do. You dont need to get a list of results and iterate through it. You can do it all in your core data fetch.
  • jsantojsanto Posts: 30New Users @
    Thanks guys, i really appreciate your help.
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