Stash is the best choice for Clash rules on iOS! Full adaptation of Clash Premium configuration. 
Stash is a rule-based proxy client with multiple proxy protocol support. Support for Rule Set, JavaScript, HTTP Rewriting, MitM, SSID Policy Groups, On-Demand Connections and other new features.

– Handle TCP / UDP / ICMP traffic and forward to any proxy server
– Route traffic to different endpoint by rule of domain, IP-CIDR, or User-Agent
– Support DNS over TCP / DNS over TLS / DNS over HTTPS
– Native UI dashboard to display HTTP / HTTPS / TCP request
– Support for Rewriting HTTP(S) requests using JavaScript
– Decrypt HTTPS traffic with Man-in-the-Middle
– Support for URL Rewrite
– Fully IPv6 supports
– Builtin DNS server with hostname mapping
– Support for overriding some of the settings of the current configuration file using Override