100 exercises to learn Rust

book/src/05_ticket_v2/13_try_from.md

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+# `TryFrom` and `TryInto`
+
+In the previous chapter we looked at the [`From` and `Into` traits](../04_traits/08_from.md), 
+Rust's idiomatic interfaces for **infallible** type conversions.  
+But what if the conversion is not guaranteed to succeed?
+
+We now know enough about errors to discuss the **fallible** counterparts of `From` and `Into`: 
+`TryFrom` and `TryInto`.
+
+## `TryFrom` and `TryInto`
+
+Both `TryFrom` and `TryInto` are defined in the `std::convert` module, just like `From` and `Into`.
+
+```rust
+pub trait TryFrom<T>: Sized {
+    type Error;
+    fn try_from(value: T) -> Result<Self, Self::Error>;
+}
+
+pub trait TryInto<T>: Sized {
+    type Error;
+    fn try_into(self) -> Result<T, Self::Error>;
+}
+```
+
+The main difference between `From`/`Into` and `TryFrom`/`TryInto` is that the latter return a `Result` type.  
+This allows the conversion to fail, returning an error instead of panicking.
+
+## `Self::Error`
+
+Both `TryFrom` and `TryInto` have an associated `Error` type.
+This allows each implementation to specify its own error type, ideally the most appropriate for the conversion
+being attempted.
+
+`Self::Error` is a way to refer to the `Error` associated type defined in the trait itself.
+
+## Duality
+
+Just like `From` and `Into`, `TryFrom` and `TryInto` are dual traits.  
+If you implement `TryFrom` for a type, you get `TryInto` for free.
+
+## References
+
+- The exercise for this section is located in `exercises/05_ticket_v2/13_try_from`