roesnera / rust_structs Goto Github PK

println! uses a reference to data, not the data itself this means that references can be passed to println! then used later dbg! prints out data but is passed ownership unless otherwise specified as &(reference) update syntax allows us to avoid unnecessary rewriting of struct fields we do not want to update similar to spread syntax in js this println! macro uses the :? to tell println to display the second_user using the debug default formatting this uses a debug format that displays each field on its own line note that because we did not change the email field, my_user is no longer valid as a whole this is because we transferred ownership of the email field to second_user when using update syntax, references used in the previous instance of the struct will be destroyed if any fields that do not implement the Copy() trait (i.e. non-primitives) are not updated, then a new instacne is created with the updated values the following code is not allowed println!("{}", my_user.email); we can however reference the fields that were not transferred to second_user this derive statement applies to the User struct this allows for the use of Debug formatting with the println! macro this is an associated function similar to a static method, this is a function associated with the User struct this function does not accept a "self" arguent it returns "Self", a new instance of User this is a Tuple Struct no field names, just data types used to create a kind of Type this is a Unit-Like Struct behaves like a () unit