Re-factor to separate Option/String handling from conditional render.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bootstrap-rs"
-version = "0.3.0"
+version = "0.4.0"
 authors = ["Thomas Gideon <cmdln@thecommandline.net>"]
 edition = "2018"
 

src/prelude/mod.rs

@@ -7,25 +7,35 @@ mod padding;
 pub use self::{border::Border, color::Color, edge::Edge, margin::Margin, padding::Padding};
 use yew::prelude::*;
 
-pub fn render_if_ne<T: PartialEq>(assign_to: &mut T, argument: T) -> ShouldRender {
-    render_if(assign_to, argument, identity, is_ne)
-}
+/// A newtype that can be helpful to work with `String` values the represent direct user input.
+///
+/// This type is convertible into `Option<String>` which makes it helpful for wrapping user input
+/// for optional fields when sent to the server. Leaving the wrapped type as a `String` value while
+/// handling input and validation helps preserve the user's text as entered so they can continue to
+/// edit or correct as needed.
+pub struct InputString<S: AsRef<str>>(pub S);
 
-pub fn render_if_opt_str<S: AsRef<str>>(
-    assign_to: &mut Option<String>,
-    argument: S,
-) -> ShouldRender {
-    render_if(assign_to, argument, opt_from_str, is_ne)
+impl<S: AsRef<str>> Into<Option<String>> for InputString<S> {
+    fn into(self) -> Option<String> {
+        let InputString(input) = self;
+        if input.as_ref().is_empty() {
+            None
+        } else {
+            Some(input.as_ref().to_owned())
+        }
+    }
 }
 
-pub fn render_if<T, A>(
-    assign_to: &mut T,
-    argument: A,
-    map: impl Fn(A) -> T,
-    assign_render: impl Fn(&mut T, &T) -> bool,
-) -> ShouldRender {
-    let argument = map(argument);
-    if assign_render(assign_to, &argument) {
+/// A convenience method for determining `ShouldRender` based on whether a value has changed, i.e.
+/// the existing and new values are not equal, and its side effect of assigning `argument` to `assign_to` for the same condition.
+///
+/// Be careful if you choose to logically `or` calls of this function together for multiple
+/// properties or state fields since short circuiting of any compound conditional may yield
+/// surprising results, specifically failure to assign some fields. For this use case, collect the
+/// results of each call into a collection then use reduce that collection to produce the result of
+/// applying `or` to all its members.
+pub fn render_if_ne<T: PartialEq>(assign_to: &mut T, argument: T) -> ShouldRender {
+    if assign_to != &argument {
         *assign_to = argument;
         true
     } else {
@@ -33,6 +43,9 @@ pub fn render_if<T, A>(
     }
 }
 
+/// A convenience method for determining which validation class to use for some input field
+/// including one that has not yet been validating, represented by the argument having a `None`
+/// value.
 pub fn valid_as_class(v: &Option<bool>) -> &'static str {
     match v {
         None => "",
@@ -41,22 +54,6 @@ pub fn valid_as_class(v: &Option<bool>) -> &'static str {
     }
 }
 
-fn identity<T>(t: T) -> T {
-    t
-}
-
-fn opt_from_str<S: AsRef<str>>(a: S) -> Option<String> {
-    if a.as_ref().is_empty() {
-        None
-    } else {
-        Some(a.as_ref().to_owned())
-    }
-}
-
-fn is_ne<T: PartialEq>(t: &mut T, a: &T) -> bool {
-    t != a
-}
-
 #[cfg(test)]
 mod test {
     use super::*;
@@ -80,7 +77,7 @@ mod test {
     #[test]
     fn render_if_opt() {
         let mut t = Some(String::from("test"));
-        let should = render_if_opt_str(&mut t, String::default());
+        let should = render_if_ne(&mut t, InputString(String::default()).into());
         assert!(should, "Should have determined to render");
         assert_eq!(t, None);
     }