Engineer

Engineer is a master builder based on Optional.

It just generates an Engineer (Builder) class for a data model.

Installation

Add following as dependencies

toml [dependencies] engineer = "0.1.3"

Get Started

```rust use engineer::Engineer;

[derive(Engineer)]

struct Identity { id: usize, username: String, firstname: Option, lastname: Option, lang_code: Option, } ```

Optional fields are not required during the initialization.

rust // Option fields are set to None. let identity = Identity::engineer(0, "immmdreza".to_string()).done();

But you can set a value for Option fields as well.

rust let identity = Identity::engineer(0, "immmdreza".to_string()) // IdentityEngineer .first_name("Arash".to_string()) // IdentityEngineer .last_name("Tofani".to_string()) // IdentityEngineer .done(); // Identity

That's all for the basics, but you can do a little customizations.

Customizations

Engineer Struct Name

Engineer struct name is {struct}Engineer (IdentityEngineer for Identity) by default, but you can change that.

```rust // ~~~ sniff ~~~

[derive(Engineer)]

[engineer(engineer_name = "IdentityBuilder")]

struct Identity { // ~~~ sniff ~~~ }

// ~~~ sniff ~~~

let identity = Identity::engineer(0, "immmdreza".to_string()) // IdentityBuilder
    .first_name("Arash".to_string()) // IdentityBuilder
    .last_name("Tofani".to_string()) // IdentityBuilder
    .done(); // Identity

```

Builder Function Name

The name of builder function is engineer by default, but guess what?

```rust // ~~~ sniff ~~~

[derive(Engineer)]

[engineer(engineername = "IdentityBuilder", builderfunc = "builder")]

struct Identity { // ~~~ sniff ~~~ }

// ~~~ sniff ~~~

let identity = Identity::builder(0, "immmdreza".to_string())
// ~~~ sniff ~~~

```

You want to use this as new function:

```rust // ~~~ sniff ~~~

[derive(Engineer)]

[engineer(engineername = "IdentityBuilder", builderfunc = "new")]

struct Identity { // ~~~ sniff ~~~ }

// ~~~ sniff ~~~

let identity = Identity::new(0, "immmdreza".to_string())
// ~~~ sniff ~~~

```

Default value for Options

You can set a default value for option fields.

This value is used if you don't set any other for them.

```rust // ~~~ sniff ~~~

[derive(Engineer)]

[engineer(engineername = "IdentityBuilder", builderfunc = "new")]

struct Identity { // ~~~ sniff ~~~ #[engineer(defaultvalue = "\"fa\".tostring()")] lang_code: Option, }

// ~~~ sniff ~~~

let identity = Identity::new(0, "immmdreza".to_string());

identity.lang_code // Some("fa")

```

Alternatively, you can use default to set Some(Default::default) instead of None if any other value is not given.

rust // ~~~ sniff ~~~ #[engineer(default)] luck_number: Option<i32>, // Some(0) // ~~~ sniff ~~~

Retype

You can change types requested in builder processes.

```rust // ~~~ sniff ~~~

[derive(Engineer)]

[engineer(builder_func = "new")]

struct Identity { // ~~~ sniff ~~~ #[engineer(retype(to = "impl Into", re = ".into()"))] // ^ ^ // | Requested type in public. // | // | How we recover to original type. username: String, // ~~~ sniff ~~~ }

// ~~~ sniff ~~~

let identity = Identity::new(0, "immmdreza"); // .to_string() is not needed.
// ~~~ sniff ~~~

```

Alternatively, for str retypes (like example above), you can use a shorthand str_retype.

rust // ~~~ sniff ~~~ #[engineer(str_retype)] username: String, // ~~~ sniff ~~~

Also you can use retypes globally.

```rust

[derive(Engineer)]

[engineer(builder_func = "new", retype(from = "String", to = "impl Into", re = ".into()"))]

struct Identity { // ~~~ sniff ~~~ } ```

Or additionally for String retypes:

```rust

[derive(Engineer)]

[engineer(builderfunc = "new", strretype)]

struct Identity { // ~~~ sniff ~~~ } ```

Both codes above will retype all String fields into impl Into<String> in public api.

Final result

```rust

[derive(Engineer)]

[engineer(builderfunc = "new", strretype)]

struct Identity { id: usize, username: String, firstname: String, lastname: Option, #[engineer(strretype, defaultvalue = "\"fa\".tostring()")] langcode: Option, }

fn print_identity(ident: impl Into) { let ident: Identity = ident.into(); println!("{ident:#?}"); }

fn main() { let ident = Identity::new(1, "immmdreza", "Arash").last_name("Tofani");

print_identity(ident);
// Identity {
//     id: 1,
//     username: "immmdreza",
//     first_name: "Arash",
//     last_name: Some(
//         "Tofani",
//     ),
//     lang_code: Some(
//         "fa",
//     ),
// }

} ```

🧀