Getting Started

Suppose we now have a faml configuration language with the following content:

[hello]
value = 12
name = $"hello {value + 12}"

We want to use Rust to modify the hello.value property and then get the hello.name property value. Let's create a Rust project and add the faml dependency:

cargo new hello_faml
cd hello_faml
cargo add faml
cargo add anyhow

Note: Since the example code uses the anyhow library for error handling, we need to add the anyhow dependency as well.

The Cargo.toml file should contain the following dependencies:

[dependencies]
faml = "0.1"
anyhow = "1.0"

Add the example code:

use anyhow::Result;

fn main() -> Result<()> {
    let faml_str = r#"
[hello]
value = 12
name = $"hello {value + 12}"
"#;
    let mut root = faml::FamlExpr::from_str(faml_str)?;
    root["hello"]["value"].set_int(30);
    let name = root["hello"]["name"].evaluate()?.as_str();
    println!("{}", name); // hello 42
    Ok(())
}

After execution, it will print the hello.name property value: hello 42

Code Explanation

1. First, we import the anyhow::Result type for error handling
2. Use faml::FamlExpr::from_str() to parse the faml string
3. Modify the value to 30 through root["hello"]["value"].set_int(30)
4. Calculate and get the name value through root["hello"]["name"].evaluate()?.as_str()
5. Since value is modified to 30, the result of the expression value + 12 is 42, so the final output is hello 42