validation builder additions

src/validation_builder.rs

@@ -1,4 +1,4 @@
-use crate::controls::ValidationFn;
+use crate::{controls::ValidationFn, FormToolData};
 use std::fmt::Display;
 
 /// A helper builder that allows you to specify a validation function
@@ -8,23 +8,25 @@ use std::fmt::Display;
 /// closures, but for simple validation function this builder can be helpful
 ///
 /// Validations are run in the order that they are called in the builder.
-pub struct ValidationBuilder<T: 'static> {
+pub struct ValidationBuilder<FD: FormToolData, T: 'static> {
     /// The name of the field, for error messages.
     name: String,
+    /// The getter function for the field to validate.
+    field_fn: Box<dyn Fn(&FD) -> &T + 'static>,
     /// The functions to be called when validating.
     functions: Vec<Box<dyn Fn(&str, &T) -> Result<(), String> + 'static>>,
 }
 
-impl<T: 'static> Default for ValidationBuilder<T> {
-    fn default() -> Self {
+impl<FD: FormToolData, T: 'static> ValidationBuilder<FD, T> {
+    /// Creates a new empty [`ValidationBuilder`] on the given field.
+    pub fn for_field(field_fn: impl Fn(&FD) -> &T + 'static) -> Self {
         ValidationBuilder {
             name: String::from("Field"),
+            field_fn: Box::new(field_fn),
             functions: Vec::new(),
         }
     }
-}
 
-impl<T: 'static> ValidationBuilder<T> {
     /// The name of the field that is being validated.
     ///
     /// This is the name that will be used for error messages.
@@ -33,9 +35,19 @@ impl<T: 'static> ValidationBuilder<T> {
         self
     }
 
+    /// Adds a custom validation function.
+    ///
+    /// The function should take the value as an argument and return
+    /// a [`Result<(), String>`], just like any other validation function.
+    pub fn custom(mut self, f: impl ValidationFn<T>) -> Self {
+        self.functions.push(Box::new(move |_name, value| f(value)));
+        self
+    }
+
     /// Builds the action validation function.
-    pub fn build(self) -> impl ValidationFn<T> {
-        move |value| {
+    pub fn build(self) -> impl ValidationFn<FD> {
+        move |form_data| {
+            let value = (self.field_fn)(form_data);
             for f in self.functions.iter() {
                 match f(self.name.as_str(), value) {
                     Ok(()) => {}
@@ -47,7 +59,7 @@ impl<T: 'static> ValidationBuilder<T> {
     }
 }
 
-impl ValidationBuilder<String> {
+impl<FD: FormToolData> ValidationBuilder<FD, String> {
     /// Requires the field to not be empty.
     pub fn required(mut self) -> Self {
         self.functions.push(Box::new(move |name, value| {
@@ -75,7 +87,7 @@ impl ValidationBuilder<String> {
     /// Requires the field's length to be less than or equal to `min_len`.
     pub fn max_len(mut self, max_len: usize) -> Self {
         self.functions.push(Box::new(move |name, value| {
-            if value.len() < max_len {
+            if value.len() > max_len {
                 Err(format!("{} must be <= {} characters", name, max_len))
             } else {
                 Ok(())
@@ -85,7 +97,7 @@ impl ValidationBuilder<String> {
     }
 }
 
-impl<T: PartialOrd<T> + Display + 'static> ValidationBuilder<T> {
+impl<FD: FormToolData, T: PartialOrd<T> + Display + 'static> ValidationBuilder<FD, T> {
     /// Requires the value to be at least `min_value` according to
     /// `PartialOrd`.
     pub fn min_value(mut self, min_value: T) -> Self {
@@ -113,7 +125,7 @@ impl<T: PartialOrd<T> + Display + 'static> ValidationBuilder<T> {
     }
 }
 
-impl<T: PartialEq<T> + Display + 'static> ValidationBuilder<T> {
+impl<FD: FormToolData, T: PartialEq<T> + Display + 'static> ValidationBuilder<FD, T> {
     /// Requires the field to be in the provided whitelist.
     pub fn whitelist(mut self, whitelist: Vec<T>) -> Self {
         self.functions.push(Box::new(move |name, value| {