start to add functionality to db

src/lib.rs

@@ -22,9 +22,14 @@ fn impl_from_args(input: &syn::DeriveInput) -> TokenStream {
     let errors = &Errors::default();
     let type_attrs = &TypeAttrs::parse(errors, input);
     let mut output_tokens = match &input.data {
-        syn::Data::Struct(ds) => {
-            impl_from_args_struct(errors, &input.ident, type_attrs, &input.generics, ds)
-        }
+        syn::Data::Struct(ds) => impl_from_args_struct(
+            errors,
+            &input.vis,
+            &input.ident,
+            type_attrs,
+            &input.generics,
+            ds,
+        ),
         syn::Data::Enum(_) => {
             errors.err(input, "`#[derive(VennDB)]` cannot be applied to enums");
             TokenStream::new()
@@ -41,6 +46,7 @@ fn impl_from_args(input: &syn::DeriveInput) -> TokenStream {
 /// Implements `VennDB` for a `#[derive(VennDB)]` struct.
 fn impl_from_args_struct(
     errors: &Errors,
+    vis: &syn::Visibility,
     name: &syn::Ident,
     type_attrs: &TypeAttrs,
     _generic_args: &syn::Generics,
@@ -69,13 +75,31 @@ fn impl_from_args_struct(
         None => format_ident!("{}DB", name),
     };
 
+    let db_doc = format!(
+        "An in-memory database for storing instances of [`{}`], generated by `#[derive(VennDB)]`.",
+        name
+    );
     quote! {
-        #[non_exhaustive]
-        struct #name_db;
+        #[doc=#db_doc]
+        #vis struct #name_db {
+            rows: Vec<#name>,
+        }
 
         impl #name_db {
-            fn new() -> Self {
-                Self
+            #vis fn new() -> Self {
+                Self {
+                    rows: Vec::new(),
+                }
+            }
+
+            /// Return the number of rows in the database.
+            #vis fn len(&self) -> usize {
+                self.rows.len()
+            }
+
+            /// Return `true` if the database is empty.
+            #vis fn is_empty(&self) -> bool {
+                self.rows.is_empty()
             }
         }
 

venndb-usage/src/main.rs

@@ -3,7 +3,7 @@
 use venndb::VennDB;
 
 #[derive(Debug, VennDB)]
-struct Employee {
+pub struct Employee {
     id: u32,
     name: String,
     is_manager: bool,
@@ -12,7 +12,7 @@ struct Employee {
     department: Department,
 }
 
-#[derive(Debug)]
+#[derive(Debug, PartialEq)]
 pub enum Department {
     Engineering,
     Sales,
@@ -33,3 +33,32 @@ fn main() {
 
     let _db = EmployeeDB::new();
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_employee() {
+        let employee = Employee {
+            id: 1,
+            name: "Alice".to_string(),
+            is_manager: true,
+            is_admin: false,
+            is_active: true,
+            department: Department::Engineering,
+        };
+        assert_eq!(employee.id, 1);
+        assert_eq!(employee.name, "Alice");
+        assert!(employee.is_manager);
+        assert!(!employee.is_admin);
+        assert!(employee.is_active);
+        assert_eq!(employee.department, Department::Engineering);
+    }
+
+    #[test]
+    fn test_employee_db_empty_len() {
+        let db = EmployeeDB::new();
+        assert_eq!(db.len(), 0);
+    }
+}