Câu hỏi phỏng vấn Objective-C
Câu hỏi

What was wrong with the NSEnumerator techniq...

Câu trả lời

The main issues with NSEnumerator were:

  1. Performance overhead: Using NSEnumerator involves creating an object to represent the enumeration and calling a method on it for every single iteration. This incurs message send overhead for each iteration, which can be inefficient, especially for large collections[1][2].

  2. Lack of language support: NSEnumerator uses a separate object and method calls to perform enumeration, which is not as tightly integrated with the language syntax compared to modern enumeration techniques[2].

To address these shortcomings, Apple introduced NSFastEnumeration in OS X Leopard and iOS 2.0. NSFastEnumeration provides a more efficient and convenient way to enumerate collections:

  • Reduced overhead: NSFastEnumeration leverages native language support to minimize message sends. It creates a struct to represent the enumeration state and repeatedly calls a single method (countByEnumeratingWithState:objects:count:) on the col...
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What is Key-Value-Coding and Key-Value-Observing in Objective-C?

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What are the reasons for using NSOperationQueue over GCD and vice versa?

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What is the difference between ARC (automatic reference counting) and GC (garbage collection)?

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