LEARNINGS.md

• modules don't implicitly include other files in the filesystem.
• json (de)serialization is specified via an annotation.
• https://stackoverflow.com/a/68795912
• Use Option<...> for fields that may not exist when JSON (de)serialization.
• https://serde.rs/lifetimes.html
• String is a mutable reference to a string on the heap?
• use after move

struct Foo {
  a: Option<i64>,
  b: Option<i64>,
}
...
let foo = Foo {
  a: 1,
  b: 2,
}

// This is fine
let a = foo.a;
let b = foo.b;

// ERROR - use after move on second line.
// let a = foo.a.unwrap();
// let b = foo.b.unwrap(); // ERROR

This is fine because a copy of foo happens. But, this breaks if in the let a line, you call a method that takes ownership of foo e.g., .unwrap().

TODOs

• Need to better understand the proper patterns of dealing with Option i.e., avoiding unwrap().

  • is it if let Some(foo)? Or some use of map?
  • https://stackoverflow.com/questions/64996954/how-can-i-pull-data-out-of-an-option-for-independent-use
  • unwrap() and expect() take ownership of self.
  • AH!!! I bet I need to use a constructor function that takes ownership!

  error[E0507]: cannot move out of `fields.tags` which is behind a shared reference
  --> src/main.rs:64:20
   |
  

64 | let tags = fields.tags.unwrap(); | ^^^^^^^^^^^ move occurs because fields.tags has type std::option::Option<std::vec ::Vec<std::string::String>>, which does not implement the Copy trait | help: consider borrowing the Option's content | 64 | let tags = fields.tags.as_ref().unwrap(); | +++++++++