Predicates and sorting in iOS Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an NSPredicate in Swift?

An NSPredicate is a way to filter collections or Core Data fetch requests by defining conditions that items must meet. Think of it like a filter that only lets through items matching certain rules.

beginner

How do you create a predicate to find names starting with "A"?

You create it like this: NSPredicate(format: "name BEGINSWITH[c] %@", "A"). This means it looks for names starting with 'A', ignoring case.

beginner

What is NSSortDescriptor used for?

NSSortDescriptor tells Swift how to sort a list of items. For example, you can sort by a property like 'age' in ascending or descending order.

intermediate

How do you sort an array of people by age descending using NSSortDescriptor?

You create a sort descriptor like this: NSSortDescriptor(key: "age", ascending: false) and use it to sort the array.

intermediate

Why use predicates and sort descriptors together?

Using predicates filters your data to only what you want, and sort descriptors organize that filtered data in the order you want. Together, they help you get exactly the right data, nicely ordered.

What does NSPredicate do in Swift?

A Filters data based on conditions

B Sorts data in ascending order

C Creates user interface elements

D Manages memory allocation

NSPredicate is used to filter data by specifying conditions.

Which of these is the correct way to create a predicate to find items where 'age' is greater than 18?

A NSPredicate(format: "age > 18")

B NSPredicate(format: "age >= 18")

C NSPredicate(format: "age < 18")

D NSPredicate(format: "age == 18")

The predicate format "age > 18" filters for ages greater than 18.

What does NSSortDescriptor(key: "name", ascending: true) do?

A Filters items with key 'name'

B Filters items with name 'true'

C Sorts items by name in descending order

D Sorts items by name in ascending order

It sorts items by the 'name' property in ascending order.

How can you combine multiple sort descriptors?

A Chain them with '+' operator

B Put them in an array and apply together

C Use only one sort descriptor at a time

D Use NSPredicate instead

Multiple NSSortDescriptors can be combined in an array to sort by multiple keys.

Which is true about predicates and sorting?

A Both sort data

B Predicates order data; sorting filters data

C Predicates filter data; sorting orders data

D Both filter data

Predicates filter data by conditions; sorting arranges data order.

Explain how you would filter a list of contacts to only those whose names start with 'J' and then sort them by last name ascending.

Think about how to write the predicate format and then create a sort descriptor.

Describe the difference between NSPredicate and NSSortDescriptor and how they work together in data handling.

Imagine filtering a list first, then arranging it.