摘要：
继续说说ios不同版本之间的适配
先说一个东西：在xcode当中有一个东西叫targets，苹果的官方文档是这样说的：
A target specifies a product to build and contains the instructions for building the product from a set of files in a project or workspace. A target defines a single product; it organizes the inputs into the build system—the source files and instructions for processing those source files—required to build that product. Projects can contain one or more targets, each of which produces one product.(省略若干字)
简单翻译过来就是一个target详细说明了要构建的 阅读全文
