vendor/handlebars-5.1.2/examples/render.rs

extern crate env_logger;
extern crate handlebars;

#[macro_use]
extern crate serde_derive;
extern crate serde_json;

use serde_json::value::{Map, Value as Json};
use std::error::Error;

use handlebars::{
    to_json, Context, Handlebars, Helper, JsonRender, Output, RenderContext, RenderError,
    RenderErrorReason,
};

// define a custom helper
fn format_helper(
    h: &Helper,
    _: &Handlebars,
    _: &Context,
    _: &mut RenderContext,
    out: &mut dyn Output,
) -> Result<(), RenderError> {
    // get parameter from helper or throw an error
    let param = h
        .param(0)
        .ok_or(RenderErrorReason::ParamNotFoundForIndex("format", 0))?;
    write!(out, "{} pts", param.value().render())?;
    Ok(())
}

// another custom helper
fn rank_helper(
    h: &Helper,
    _: &Handlebars,
    _: &Context,
    _: &mut RenderContext,
    out: &mut dyn Output,
) -> Result<(), RenderError> {
    let rank = h.param(0).and_then(|v| v.value().as_u64()).ok_or(
        RenderErrorReason::ParamTypeMismatchForName("rank", "0".to_string(), "u64".to_string()),
    )? as usize;
    let total = h
        .param(1)
        .as_ref()
        .and_then(|v| v.value().as_array())
        .map(|arr| arr.len())
        .ok_or(RenderErrorReason::ParamTypeMismatchForName(
            "rank",
            "1".to_string(),
            "array".to_string(),
        ))?;
    if rank == 0 {
        out.write("champion")?;
    } else if rank >= total - 2 {
        out.write("relegation")?;
    } else if rank <= 2 {
        out.write("acl")?;
    }
    Ok(())
}

static TYPES: &'static str = "serde_json";

// define some data
#[derive(Serialize)]
pub struct Team {
    name: String,
    pts: u16,
}

// produce some data
pub fn make_data() -> Map<String, Json> {
    let mut data = Map::new();

    data.insert("year".to_string(), to_json("2015"));

    let teams = vec![
        Team {
            name: "Jiangsu Suning".to_string(),
            pts: 43u16,
        },
        Team {
            name: "Shanghai SIPG".to_string(),
            pts: 39u16,
        },
        Team {
            name: "Hebei CFFC".to_string(),
            pts: 27u16,
        },
        Team {
            name: "Guangzhou Evergrand".to_string(),
            pts: 22u16,
        },
        Team {
            name: "Shandong Luneng".to_string(),
            pts: 12u16,
        },
        Team {
            name: "Beijing Guoan".to_string(),
            pts: 7u16,
        },
        Team {
            name: "Hangzhou Greentown".to_string(),
            pts: 7u16,
        },
        Team {
            name: "Shanghai Shenhua".to_string(),
            pts: 4u16,
        },
    ];

    data.insert("teams".to_string(), to_json(&teams));
    data.insert("engine".to_string(), to_json(TYPES));
    data
}

fn main() -> Result<(), Box<dyn Error>> {
    env_logger::init();
    // create the handlebars registry
    let mut handlebars = Handlebars::new();

    // register template from a file and assign a name to it
    handlebars.register_template_file("table", "./examples/render/template.hbs")?;

    // register some custom helpers
    handlebars.register_helper("format", Box::new(format_helper));
    handlebars.register_helper("ranking_label", Box::new(rank_helper));

    // make data and render it
    let data = make_data();
    println!("{}", handlebars.render("table", &data)?);
    Ok(())
}