macOS Sum rows with certain values

[Helikutt]

Hi

I've been looking a solution to my problem. I red this document:
http://developer.apple.com/document...l/KeyValueCoding/Concepts/ArrayOperators.html

- but I still have no glue how to do this.

I have an Array, which is bind to Person class.
Person class has 2 values: "Name" and "Total"

I want to sum "Total" column where name equals someName.
I mean I don't want to sum whole column but only the rows with certain "Name" value.

I probably have to use loop function but I'm not sure how to do this.

I would be very thanful if anyone can help me with this.

Helikutt

 

[Bakerman]

Use filteredArrayUsingPredicate: to filter out only persons with the name you are looking for. Then use valueForKeyPath"@sum.Total" on the resulting array to get the value you are looking for.

BTW, it is standard practice to use lowercase for the initial letter in property names.

 

[Helikutt]

Thanx for reply, I will try this out.

The property names are actually starting with lowercase in my class file.
I don't know why I typed them uppercase here, I'll be more careful next time.

Helikutt

 

[Helikutt]

Hi again

Here is the code I figured out so far - I got 2 errors.

- (double)johnTotal {

	NSString *userName = @"John";
	
	NSPredicate *johnTotalPredicate = [NSPredicate predicateWithFormat:@"person.name like %@", userName];
	NSArray *jTotal = [array filteredArrayUsingPredicate:johnTotalPredicate];

I get an error here saying: 'array' undeclared (first use in this function)
I believe I should declare my Users array here and change the array to Users array - but I'm not sure how to do that.

	return [jTotal valueForKeyPath:@"@sum.total"];
}

Another error here: incompatible types in return
How should I avoid that.

- (void)setJohnTotal:(double)aJohnTotal {
	johnTotal = aJohnTotal;
}

Am I close or not?
Again, I'd be very thankful if someone would help me out here.

Helikutt

 

[Helikutt]

I've been reading everything about filteredArrayUsingPredicate: , but I'm still not sure how to use it.

Anyone willing to help

 

[Helikutt]

I'm continuing my monologue here -

I upgraded my little database a bit following tutorials from cocoacast.
I now have a document based cocoa application.
Added save & open funcion and a relationship.
I now have to classes - Person and Total

Person class holds single value "name"
Total class holds 3 values "date", "person" and "total".

I've made some progress - 2 previous errors are gone but I have a new one at the end:
error: incompatible types in assignment

So basically I'm still in the same place.
If anyone notice a problem that causes the error, please let me know.


Problematic code:

- (double)johnTotal {

	NSString *userName = @"John";
	
	NSPredicate *johnTotalPredicate = [NSPredicate predicateWithFormat:@"person.name like %@", userName];
	NSArray *jTotal = [totals filteredArrayUsingPredicate:johnTotalPredicate];

	return [jTotal valueForKeyPath:@"@sum.total"];
}

 

[mysticwhiskey]

I'm continuing my monologue here -

I upgraded my little database a bit following tutorials from cocoacast.
I now have a document based cocoa application.
Added save & open funcion and a relationship.
I now have to classes - Person and Total

Person class holds single value "name"
Total class holds 3 values "date", "person" and "total".

I've made some progress - 2 previous errors are gone but I have a new one at the end:
error: incompatible types in assignment

So basically I'm still in the same place.
If anyone notice a problem that causes the error, please let me know.


Problematic code:

- (double)johnTotal {

	NSString *userName = @"John";
	
	NSPredicate *johnTotalPredicate = [NSPredicate predicateWithFormat:@"person.name like %@", userName];
	NSArray *jTotal = [totals filteredArrayUsingPredicate:johnTotalPredicate];

	return [jTotal valueForKeyPath:@"@sum.total"];
}

Hi,

I think it might be the last line that's causing the problem:

return [jTotal valueForKeyPath:@"@sum.total"];

since the valueForKeyPath method returns an object, but your method is defined as returning a double. Maybe the following will make it work:

return [[jTotal valueForKeyPath:@"@sum.total"] doubleValue];

Edit: if this doesn't work, it might be useful to split the last line into two so you can see if the valueForKeyPath method is returning a non-nil number object:

NSNumber* myTotal = [jTotal valueForKeyPath:@"@sum.total"];
if (myTotal != nil)
    return [myTotal doubleValue];
else
    return 0;

 

[Helikutt]

thanx mysticwhiskey, it works.

Now I run into another problem. How to make it to update the johnTotal when I insert new entry to the table. At the moment it calculates when I save and reopen the document.

In my total class I have a value that is calculated and is updated using

[Total setKeys:[NSArray arrayWithObjects"value", @"tax", nil]
triggerChangeNotificationsForDependentKey"total"];

I'm trying to figure this one out myself.

Thanx again Bakerman and mysticwhiskey

 

[Eraserhead]

Worst case you do it without bindings, i.e. load the table manually and use the delegate to check when the selection is changed.

 

[Helikutt]

Hi again

I just wanted to thank you all who helped me with this issue.

I managed to solve the update problem using
willChangeValueForKey: and didChangeValueForKey:

Everything works perfectly.

Thanx again