charts是用swift编写的
第一步oc与swift混编
https://www.jianshu.com/p/814e71e19175
https://www.cnblogs.com/mazhiqiang/p/5557002.html
http://blog.csdn.net/zlj_jeck/article/details/51503937
http://www.cocoachina.com/ios/20170410/19022.html
第二步导入charts（cathage）
https://www.jianshu.com/p/562b307cc0ef
image.png
github "danielgindi/Charts" ~>3.0.4
