async
https://github.com/duemunk/async
syntactic sugar in swift for asynchronous dispatches in grand central dispatch (gcd)
这是一个swift中gcd的语法糖库。
async sugar looks like this:
async使用起来就像这样子：
instead of the familiar syntax for gcd:
替换了下面的这种显示方式：
install
benefits
less verbose code 更少的冗余代码
less code indentation 更少的缩进风
things you can do
supports the modern queue classes:
支持常用的queue类：
chain as many blocks as you want:
你可以将不同的block链接起来使用：
store reference for later chaining:
也可以分开使用：
custom queues:
自定义queue：
dispatch block after delay:
延时执行：
cancel blocks that aren't already dispatched:
取消没有启动的线程：
wait for block to finish – an ease way to continue on current queue after background task:
等待一个block运行结束：
how does it work
the way it work is by using the new notification api for gcd introduced in os x 10.10 and ios 8. each chaining block is called when the previous queue has finished.
本库使用了 ios 8 提供的通知 api 来完成相关功能，每一个block都会在上一个block执行完了之后继续执行：
the syntax part of the chaining works by having class methods on the <code>async</code> object e.g. <code>async.main {}</code> which returns a struct. the struct has matching methods e.g. <code>thestruct.main {}</code>.
known bugs
modern gcd queues don't work as expected in the ios simulator. see issues 13, 22.
known improvements
the <code>dispatch_block_t</code> can't be extended. workaround used: wrap <code>dispatch_block_t</code> in a struct that takes the block as a property.
bonus stuff
there is also a wrapper for <code>dispatch_apply()</code> for quick parallelisation of a <code>for</code> loop.
note that this function returns after the block has been run all 100 times i.e. it is not asynchronous. for asynchronous behaviour, wrap it in a an <code>async</code> block like <code>async.main{ apply.background(100) { ... } }</code>.