Rust 101 – 12: Traits

February 19, 2024, 12:57 am

≫ Next: Rust 101 – 13: Type Parameters and Associated Types

Explaining what a trait is, and how to use it. A trait is a bit like an Interface in Java or Go, or an Abstract Base Class in C++ or Python, but it can be used to define behaviour at compile-time as well as at run-time. We go through an example of why you might want to write a “generic” function – one that works for lots of different types, and if so, how you need to be able to say what the types can do if you want to write the body of the function. Traits are a way of saying what a type can do.

Links:

Slides: Rust 101 – 12: Traits and slices
Exercises: 101-rs.tweede.golf/A3-traits-generics/mod.html

The course materials for this series are developed by tweede golf. You can find more information at github.com/tweedegolf/101-rs and you can sponsor the work at github.com/sponsors/tweedegolf. They are released under the Creative Commons Attribution Share Alike 4.0 International license.

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Rust 101 – 13: Type Parameters and Associated Types

February 22, 2024, 1:43 am

≫ Next: Rust 101 – 14: Some standard library traits

≪ Previous: Rust 101 – 12: Traits

Following on from video 12, looking at how to add type information to traits, to make them flexible enough to describe generic code with different types, for example how to add a u32 to a u64 and return a u128, without defining a whole new trait for every combination of types.

Links:

Slides: Rust 101 – 13: Type Parameters and Associated Types
Exercises: 101-rs.tweede.golf/A3-traits-generics/mod.html

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Rust 101 – 14: Some standard library traits

March 7, 2024, 1:47 am

≫ Next: Rust 101 – 15: Lifetime bounds

≪ Previous: Rust 101 – 13: Type Parameters and Associated Types

A tour of some of the most interesting traits in the standard library including Add etc. to overload operators, Sized, Sync and Send for telling the compiler special things about your type, Clone and Copy for copying things, Into and From for converting, AsRef and AsMut for making your APIs flexible, Default for easy creation, and Drop which is called when your object is deleted. Also a few words on what happens when you call a function with generic type parameters.

Series: 1: Intro, 2: Language basics, 3: Memory and ownership, 4: Exercises A1, 5: References, 6: Structs and Enums, 7: Panic and Result, 8: Methods, 9: Vec and Box, 10: Strings, 11: Exercises A2, 12: Traits, 13: Type Params, 14: std Traits

Links:

Slides: Rust 101 – 14: Some standard library traits
Exercises: 101-rs.tweede.golf/A3-traits-generics/mod.html

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Rust 101 – 15: Lifetime bounds

March 14, 2024, 2:27 am

≫ Next: Rust 101 – 16: Exercises for module A3 (part 1)

≪ Previous: Rust 101 – 14: Some standard library traits

This time we tackle one of the most tricky areas for a new Rust programmer: lifetimes. The key point is that when we add lifetime bounds ('a or similar) to a function signature, this is not to help Rust compile our function: it’s to help Rust understand the lifetime of our return values, so that it knows how to compile the code that calls this function. The lifetime bounds tell the compiler about the references we return – specifically, how they relate to the references that were passed in.

Links:

Slides: Rust 101 – 14: Some standard library traits
Exercises: 101-rs.tweede.golf/A3-traits-generics/mod.html

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Rust 101 – 16: Exercises for module A3 (part 1)

March 23, 2024, 9:34 am

≫ Next: Automated backups from Signal to Nextcloud

≪ Previous: Rust 101 – 15: Lifetime bounds

Going through some exercises on Rust traits, designing a customised version of Vec.

Links:

Slides: Rust 101 – module A3
Exercises: 101-rs.tweede.golf/A3-traits-generics/mod.html

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Automated backups from Signal to Nextcloud

March 29, 2024, 3:17 am

≫ Next: Rust 101 – 17: Exercises for module A3 (part 2)

≪ Previous: Rust 101 – 16: Exercises for module A3 (part 1)

DON’T DO THIS: the Signal app has the ability to make daily backups of your messages, and when you choose a folder to backup into, you can choose “Nextcloud” as the device, then choose a Nextcloud folder to back up to.

Don’t do that.

Although the above worked for me for a long time, a few weeks ago, Signal started making 0-byte files for all my backups, and merrily deleting the old ones.

Instead, choose a normal folder on your phone and ask Signal to back up to there.

Then open the Nextcloud app, go to Settings, Auto-uploads, and add a custom folder to auto-upload. For Local Folder, choose the folder you just told Signal to back up into, and for the Remote Folder choose somewhere in Nextcloud to store your backups.

Nextcloud will automatically notice whenever a new backup file appears and copy it to your server.

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