enableAPNs method Null safety

void enableAPNs(
  1. String certName
)

开启苹果推送,具体申请证书和上传流程请参考文档 http://docs-im.easemob.com/im/ios/apns/deploy

Implementation

void enableAPNs(String certName) {
  _enableAPNS = true;
  _apnsCertName = certName;
}