IOS: reprint: synchronous, asynchronous, parallel, serial-detailed

<span id="Label3"></p><span style="font-size: 15px;"><span style="font-size: 15px;">Understanding GCD-related synchronization (synchronization) \ async (asynchronization), serial (serial) \ Parallel (concurrency) Concepts in IOS development</span></span><span style="font-size: 15px;"><span style="font-size: 15px;">November 21, 2014 iosasynchronization, concurrency, GCD, iOS, serial, synchronization, serial, synchronous, concurrent, Asynchronous</span></span><p><p><span style="font-size: 15px;">In IOS development process, often need to use multithreading technology, GCD is commonly used to implement multi-threading technology, which is popular because of the simplicity of the BOTTOM.</span></p></p><p><p><span style="font-size: 15px;">In GCD technology, concepts such as synchronous (synchronization) \ Asynchronous (asynchronization), serial (serial) \ Parallel (concurrency) are often confusing and poorly understood. These two concepts are explained in the simplest possible terms.</span></p></p><p><p><span style="font-size: 15px;">Synchronization and Asynchrony are related to the order of execution between the current code flow (that is, the current thread) and the tasks in the join Queue. Adding a task to a queue synchronously blocks the current thread until the task that is synchronized to the queue has finished returning before the current code flow is executed, the task that is added asynchronously to the queue does not block the current thread, and the task is added to the queue without waiting for the task to complete and immediately executes the current code FLOW. Examples are as Follows:</span></p></p>