18. Grand Central Dispatch for Performance
Many apps have challenging performance requirements, involving multiple processor-intensive and high-latency tasks that need to take place simultaneously. This chapter demonstrates the negative effects of blocking the main queue, which makes the user interface slow or completely unusable—not at all desirable for a good user experience. It then examines tools supported by iOS that enable the programmer to perform tasks “in the background,” meaning that a processing task will take place and not directly delay updating the user interface. Apple provides several tools with varying degrees of control over how background tasks are accomplished.
Concurrent programming is frequently done using threads. It can ...
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