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readme.md

@@ -11,4 +11,82 @@ composer install
 composer test
 ```
 
-I want to write a blog post about how to use this, practically. When that's done, I will replace this paragraph with a link to the post.
+## Defining types
+
+We support most of the built-in types:
+
+```php
+use App\Profile;
+use Pre\PropTypes;
+
+$profile = Profile::find(1);
+
+$definitions = [
+    "name" => PropTypes::string()->isRequired(),
+    "age" => PropTypes::int(),
+    "rating" => PropTypes::float(),
+    "permissions" => PropTypes::arrayOf(PropTypes::string()),
+    "thumbnail" => PropTypes::either(
+        PropTypes::string(), // uri
+        PropTypes::resource(), // file handle
+    ),
+    "profile" => PropTypes::objectOf(Profile::class)->isRequired(),
+    "notifier" => PropTypes::closure()->isRequired(),
+    "isAdmin" => PropTypes::bool()->isRequired(),
+];
+
+$properties = [
+    "name" => "Joe",
+    "profile" => $profile,
+    "notifier" => function($message) use ($profile) {
+        $profile->notify($message);
+    },
+    "isAdmin" => false,
+];
+
+try {
+    PropTypes::validate($definitions, $properties);
+} catch (InvalidArgumentException $e) {
+    // ...handle the error
+}
+```
+
+- `isRequired` will ensure the value is present in the accompanying properties array
+- `either` allows one or more types (preferably two distinct types) for comparison
+
+There are also variations on these:
+
+- `PropTypes::array()` expects any array values, without a specific type
+- `PropTypes::boolean()` is the same as `PropTypes::bool()`
+- `PropTypes::integer()` is the same as `PropTypes::int()`
+- `PropTypes::double()` expects double values
+- `PropTypes::iterable()` expects any iterable values
+- `PropTypes::numeric()` expects any numeric values
+- `PropTypes::object()` expects any object values, without a specific type
+
+## Validating types
+
+We don't automatically validate props – this must be done by the consumer. And example Phpx render method demonstrates this:
+
+```php
+use Pre\PropTypes;
+use function Pre\Phpx\Html\render as renderHTML;
+
+function render($type, $props = []) {
+    $props = (array) $props;
+
+    if (class_exists($type)) {
+        if (method_exists($type, "propTypes")) {
+            PropTypes::validate($type::propTypes(), $props);
+        }
+
+        if (method_exists($type, "defaultProps")) {
+            $props = array_merge($type::defaultProps(), $props);
+        }
+    }
+
+    return renderHTML($type, $props);
+}
+
+render("App\\Custom\\Component");
+```