In the 2019 Rust Survey, a lot of people were asking for video content covering intermediate Rust content. So in this first video (possibly of many), we're going to investigate a case where you need multiple explicit lifetime annotations. We explore why they are needed, and why we need more than one in this particular case. We also talk about some of the differences between the string types and introduce generics over a self-defined trait in the process. And don't worry, I know that what we're implementing exists in the standard library :) 0:00:00 Introduction 0:03:36 Start a rust project 0:05:20 Struct and method definitions for StrSplit and first test 0:09:32 How you decide between a library and a binary 0:10:58 Start implementing StrSplit 0:16:15 When to use match vs if let some 0:17:10 Doesn't compile! missing lifetime specifier 0:20:33 Can I be wrong by specifying lifetimes? 0:21:25 Anonymous lifetime '_ 0:23:10 Order lifetimes based on how long they are 0:25:18 Anonymous lifetime '_ (with multiple lifetimes) 0:26:52 Compile error: lifetime of reference outlives lifetime of borrowed content 0:34:45 Static lifetime 0:41:27 Bug when a delimiter tails a string 0:48:07 What is the ref keyword and why not & 0:51:36 What's the * on the left of remainder 0:52:46 What is take() doing 0:54:48 Mutable references are one level deep 0:55:39 Solving a hang with as_mut() 0:57:49 Multiple lifetimes, implementing until_char 1:03:19 Difference between a str and a String 1:08:15 Multiple lifetimes (continued) 1:15:24 Generic delimiter (Delimiter trait) 1:23:14 char length utf8 1:25:30 Standard library split 1:27:39 Q&A You can find the final code at https://gist.github.com/jonhoo/2a7fdcf79be03e51a5f95cd326f2a1e8. You can watch the live version with comments at https://www.youtube.com/watch?v=Oxaex566Irg