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In the last few lessons, we've managed to make our app be able to create data in our database, as well
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as read the data that exists in our database.
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And now we're going to tackle the "U" that's updating data into our database.
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The perfect place to look at this is, of course, the part where we update that done property, and that's
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when we click and select each item.
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Now, currently, what we're doing is that we're tapping into the current item by using the
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indexPath.row property.
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So, for example, if I clicked on this first row, then the indexPath.row would be equal to zero.
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And I would go inside the itemArray which we know is a array of NSManagedObjects and I would retrieve
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the first item inside that array.
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And then I would modify it's done property or done attribute to be the opposite of what it used to be.
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So true turns false, false turns to true.
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And then I commit those changes by using the saveItem's method which simply commits the current state
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of the context with that updated attribute to our persistent container.
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Now, there's other methods that you can use.
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For example, let's grab the current selected NSManagedObject and we can say .setValue
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forKey.
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So if we know that the key that we want to change was the title, for example,
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right?
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And we want to change the title to completed for every single completed task.
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So maybe your task used to say "Save the World!"
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but when you click on it, it now is going to read "Completed."
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Then this is a method that you can use to update your NSManageObject as well.
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But remember that no matter how you decide to update your NSManageObject, you still always have to
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call context.save.
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And that's because we're doing all of our changes, all of our creating, updating, reading, and destroying
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inside our temporary context.
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And it's only once we're happy with all those changes that we call context.save and commits those changes
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to our permanent container.
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So I'm going to keep my code here as it was before because it's more succinct than using a whole bunch
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of "if else" statements and trying to use set value forKey.
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This does exactly the same thing but in far fewer lines
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and it also looks a lot neater.
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So in the next lesson, we're going to talk about the last item in crud which is how do you delete items
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from your database using Core Data.
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So for all of that and more, I'll see you on the next lesson.