Is there a way to sum the values entered into a table view cell without using Core Data? I am currently using Parse. I guess a better question would be how can I get the sum using Parse? I'm really scratching my head on this one. Hand holding may be required.
You can probably use the Key-Value Coding collection operators. Suppose the row data for the table are a bunch of instances of class Entry and are collected in an NSArray named data. Further suppose each Entry object has an NSNumber property named cost and this is what you want to sum. Then you can do so as follows:
NSNumber *sum = [data valueForKeyPath:#"#sum.cost"];
Just to be clear: this does require that the values you wish to sum are properties of the objects that are backing each row.
Related
I have been looking around everywhere online and can't seem to get a solid answer. If I have an event with multiple attributes stored in Core Data in an array and I can display all of these individual events in a tableView. Lets say one of the attributes is a date. Is there away to search for all of the events that contain a certain date and display only those in the tableView? I was thinking of using NSPredicate from what I am seeing online but I am not familiar with this. Maybe somehow find the index of the event that contains that date and only display that index? Any ideas?
Table views are designed to implement a one to one relationship with the underlying array of data. The usual approach is to use a fetchRequest to only get the data you want to display ( I personally like to have all my requests pre-defined in the data model so I can keep track of how data is accessed).
But, if your array of managed record must contain more elements than what you want to display, you should consider basing your tableView datasource responses on an intermediate array that only contains (or refers to) the objects you want to show.
For example:
let allEvents:[EventRecord] = GetAllEvents()
var filteredEvents:[EventRecord] = allEvents.filter({ $0.eventDate.isEqualToDate(dateToDisplay) })
and use filteredEvents as your underlying store for your datasource.
This will make it easy to dynamically change the filtering conditions and reload the tableview without having to go back to the database for each filter change.
I have a tableView and an array locationsArray. The locations array is filled on viewDidLoad from data in my CoreData.
I have implemented the reorder methods on the tableView and that works fine however I can't figure out how to save the reordered array back into CoreData. I've tried deleting everything in CoreData and just saving the new reorderedArray. Although this is obviously very costly resource wise it seems to just load the elements back into the array in a seemingly random order.
Is there an easy way to do this that I am missing or can you not store things in CoreData in a certain order?
Strictly saying, it is impossible to store objects in certain order. You can only set the order for retrieved objects
When you retrieve locationsArray from CoreData, you have no any guaranties about their order.
The only way - add field to your Managed Object that will be used to order your locations.
Than, on retrieval, you'll be able to use locationsArray = [locationsArray sortedArrayUsing<#WhateverYouNeed#>];.
You can, also, achieve this by using sortDescriptors property of NSFetchRequest. It will provide you with desired behaviour from the box. The only downside of it, that your NSSortDescriptor in that case cannot be defined by block, so if you ordering is using some complex approach, you'll need to sort the result with already fetched data
use the predicate to sort the array or after fetching the array from coredata sort it using
NSArray *sortedlocationarray = [filteredlocationarray sortedArrayUsingDescriptors:#[sortDescriptor]];
where filteredlocationarray is from coredata.
I have 4 values coming from json (name, ratings, reviews and Qualifications). I want to sort this data using name, reviews and qualifications one by one. But when I sort this data then remaining values are not changing in array.
Here is my code.
_arrOfDoc_name = [_arrOfDoc_name sortedArrayUsingSelector:#selector(localizedCaseInsensitiveCompare:)];
From comments:
I have to show four values on my screen which are coming from 4 different arrays. but when i sort one array then values of another arrays are not gng to sort and it displays wrong data on screen. how can i sort data of remaining arrays using its index path.
Ok, your comments explain what you're trying to do.
The best answer is to NOT use 4 different arrays. Restructure your data to have a single array that contains dictionaries. Then sort the array of dictionaries.
Failing that, you'll have to be clever. You might be able to create an array of indexes and sort that, or hand-write a sort routine that sorts all 4 arrays at once.
This question already has answers here:
What's the difference between a dictionary and an array?
(6 answers)
Closed 10 years ago.
I'm in a dilemma in terms of which of the two I should use. I will be retrieving a group of data via a restful API (returns json) and I'm not sure how I should store them before I display it on my UI View Table.
eg.
{"Events":[{"Id":5,"Name":"Event 1 2013"},{"Id":6,"Name":"Event 2 2013"}]}
I've been reading tutorials and some would use NSMutableArrays while some would use NSMutableDictionary.
How should I go about it?
BTW: I'm displaying the data on UI View table that will redirect the user to another page when tapped and if they decide to go back will have to show the previous view without reloading (uses UinavigationController)
Thanks!
EDIT:
Also, just to give you an idea on what I'm trying to do. I'm trying to follow this tutorial on splitting the data I get into section headers. On this tutorial it's using NSDictionary.
http://www.icodeblog.com/2010/12/10/implementing-uitableview-sections-from-an-nsarray-of-nsdictionary-objects/
If I use NSArray, would that affect the performance?
In NSArray - every item in the collection has an integer index, so there is an explicit order to the items. When you're retrieving/replacing/removing the stored object from the NSARRY,you need to specify the corresponding object index of that stored object.
NSDictionary - derived from the word called entry. Each entry consists of one object that represents the key and a second object that is that key’s value. Within a dictionary, the keys are unique. That is, no two keys in a single dictionary are equal (as determined by isEqual:).When you're retrieving the object from the dictionary you need to specify the key value for the objectForKey
Whenever if you're parsing the plist then NSDictionary would be ideal.You can refer apple's document here for more explanation about NSDictionary.Happy coding :)
The lookup times on NSDictionaries are faster than on NSArrays. That's one of the main advantages. Here's a link to the Apple documentation.
Generally, if you need to access data in an indexed fashion (like you need to for rows in a table) then you should use an array because you can access any specific index using indexOfObject:
Now, if you have a lot of information for each row then you should have an array of either custom objects or an array of dictionaries.
Dictionary are always faster than Arrays. Dictionary maps keys to objects, just like a hash table. It's an associative array.
For searching some value you need to iterate for arrays, in dictionary you retrieve it by key.
If you want the collection to be in some sorted order or arrival order then Array is the proper type for you.
Dictionary lacks when you end up getting two same keys.
And I feel good to use arrays for tableViews as I can directly associate row to index.
I am currently inserting records one-by-one into a table from C++ code using OCI. The data is in a hashmap of structs, I iterate over the elements of the map, binding the attributes of the struct to the columns of a record in the table (e.g.
define insert query
use OCIBindByname( ) for all the columns of record
iterate over map
assign bind variables as attributes of the struct
OCIStmtExecute
end
This is pretty slow, so I'd like to speed up by doing a bulk insert. What is a good way to do this? Should I use an array of struct to insert all the records in one OCIStmtExecute? Do you have any example code which shows how to do this?
Here is some sample code showing how I implemented this in OCI*ML. In summary, the way to do this is (say for a table with one column of integers):
malloc() a block of memory of sizeof(int) × the number of rows and populate it. This could be an array.
Call OCIBindByPos() with that pointer for *valuep and the size for value_sz.
Call OCIStmtExecute() with iters set to the number of rows from step 1
In my experience, speedups of 100× are certainly possible.
What you probably want to do is 'bulk inserts'. Bulk inserts in array are done by using ArrayBinds where you bind the data of the first row with the first structure of the array and set jumps, which generally is size of structure. After this you can just do statement execute with number of arrays. Multiple binds will create overheads, hence bulk inserts are used.
bulk insert example.txt
by
{
delimeter=',' // or any delimiter specified in your text files
size=200kb //or your size of text file
}
Use DPL(Direct Path Loading).
Refer to docs.oracle.com for more info.