From 976607faf73cc0eb6863cef704b1e99cb065e122 Mon Sep 17 00:00:00 2001
From: Andrea Zagli <azagli@libero.it>
Date: Wed, 4 Jan 2023 15:21:42 +0100
Subject: [PATCH] Callback for missing columns.

---
 examples/grid.rs |  8 ++++++++
 src/lib.rs       | 20 ++++++++++++++++++--
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/examples/grid.rs b/examples/grid.rs
index 09dc5e9..0f776a2 100644
--- a/examples/grid.rs
+++ b/examples/grid.rs
@@ -43,6 +43,10 @@ struct AppState {
 	settings: Settings,
 }
 
+fn get_not_exists(value: &serde_json::Value) -> String {
+	String::from("not exists (returned by fn)")
+}
+
 async fn index(
     data: web::Data<AppState>,
 ) -> Result<impl Responder, Error> {
@@ -78,6 +82,10 @@ async fn index(
 	col.set_align(zakgrid::Align::Right);
 	grid.add_column(col);
 
+	let mut col = zakgrid::Column::new("not_exists");
+	col.to_call = Some(get_not_exists);
+	grid.add_column(col);
+
 	let cols = grid.columns();
 
 	for (i, v) in cols.iter().enumerate() {
diff --git a/src/lib.rs b/src/lib.rs
index b161b66..c5bebac 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,6 +2,8 @@ use serde_json::Value;
 use serde_derive::Serialize;
 use tera::Tera;
 
+pub type ToCall = fn(row: &serde_json::Value) -> String;
+
 #[derive(Copy, Clone, Serialize)]
 pub enum Align {
 	Left,
@@ -14,6 +16,7 @@ pub struct Column {
 	title: String,
 	align: Align,
 	hidden: bool,
+	pub to_call: Option<ToCall>,
 }
 
 impl Column {
@@ -23,6 +26,7 @@ impl Column {
 			title: String::from(name),
 			align: Align::Left,
 			hidden: false,
+			to_call: None,
 		}
 	}
 
@@ -130,7 +134,7 @@ impl Grid {
 		String::from(tera.render("header", &context).unwrap().as_str())
 	}
 
-	pub fn row_from_json(&self, value: &serde_json::Value) -> String {
+	pub fn row_from_json(&self, row: &serde_json::Value) -> String {
 		let mut s = String::new();
 
 		let mut tera = Tera::default();
@@ -141,7 +145,19 @@ impl Grid {
 		for c in &self.columns {
 			if !c.hidden {
 				let mut context = tera::Context::new();
-				context.insert("value", &value[c.name.as_str()]);
+				match &row[c.name.as_str()] {
+					serde_json::Value::Null => {
+						match c.to_call {
+							None => context.insert("value", ""),
+							Some(call) => {
+								let v = (call)(&row);
+								context.insert("value", v.as_str());
+							}
+						}
+					},
+					_ => context.insert("value", &row[c.name.as_str()])
+				}
+
 				context.insert("align", &c.align);
 				s.push_str(tera.render("row_col", &context).unwrap().as_str());
 			}
-- 
2.49.0