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