Apple Pay _PKPaymentNetworkChinaUnionPay error

Feb 18, 2016

Undefined symbols for architecture arm64:
  "_PKPaymentNetworkChinaUnionPay", referenced from:
      -[UPAInitViewController startAPPay] in libUPAPayPlugin.a(UPAInitViewController.o)
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

原因：使用的sdk低于ios 9.2，即xcode版本低于7.2， sdk的passkit中没有PKPaymentNetworkChinaUnionPay这个变量

解决：升级xcode就可以了