diff --git a/packages/fortifier-macros/src/lib.rs b/packages/fortifier-macros/src/lib.rs
index 263faec..54a9008 100644
--- a/packages/fortifier-macros/src/lib.rs
+++ b/packages/fortifier-macros/src/lib.rs
@@ -3,6 +3,7 @@
 //! Fortifier macros.
 
 mod validate;
+mod validation;
 mod validations;
 
 use proc_macro::TokenStream;
diff --git a/packages/fortifier-macros/src/validate/field.rs b/packages/fortifier-macros/src/validate/field.rs
index c6a794b..e722a69 100644
--- a/packages/fortifier-macros/src/validate/field.rs
+++ b/packages/fortifier-macros/src/validate/field.rs
@@ -2,38 +2,36 @@ use proc_macro2::TokenStream;
 use quote::quote;
 use syn::{Field, Result};
 
-use crate::validations::{Email, Length, Url};
+use crate::{
+    validation::Validation,
+    validations::{Email, Length, Url},
+};
 
 pub struct ValidateField {
     expr: TokenStream,
-    // TODO: Consider using a trait for validations.
-    email: Option<Email>,
-    length: Option<Length>,
-    url: Option<Url>,
+    validations: Vec<Box<dyn Validation>>,
 }
 
 impl ValidateField {
     pub fn parse(expr: TokenStream, field: &Field) -> Result<Self> {
         let mut result = Self {
             expr,
-            email: None,
-            length: None,
-            url: None,
+            validations: vec![],
         };
 
         for attr in &field.attrs {
             if attr.path().is_ident("validate") {
                 attr.parse_nested_meta(|meta| {
                     if meta.path.is_ident("email") {
-                        result.email = Some(Email::parse(&meta)?);
+                        result.validations.push(Box::new(Email::parse(&meta)?));
 
                         Ok(())
                     } else if meta.path.is_ident("length") {
-                        result.length = Some(Length::parse(&meta)?);
+                        result.validations.push(Box::new(Length::parse(&meta)?));
 
                         Ok(())
                     } else if meta.path.is_ident("url") {
-                        result.url = Some(Url::parse(&meta)?);
+                        result.validations.push(Box::new(Url::parse(&meta)?));
 
                         Ok(())
                     } else {
@@ -49,26 +47,25 @@ impl ValidateField {
     pub fn error_type(&self) -> TokenStream {
         // TODO: Merge error types
 
-        if self.email.is_some() {
-            quote!(EmailError)
-        } else if self.length.is_some() {
-            quote!(LengthError<usize>)
-        } else if self.url.is_some() {
-            quote!(UrlError)
-        } else {
-            quote!(())
-        }
+        self.validations
+            .first()
+            .map(|validation| validation.error_type())
+            .unwrap_or_else(|| quote!(()))
     }
 
     pub fn sync_validations(&self) -> Vec<TokenStream> {
-        let email = self.email.as_ref().map(|email| email.tokens(&self.expr));
-        let length = self.length.as_ref().map(|length| length.tokens(&self.expr));
-        let url = self.url.as_ref().map(|url| url.tokens(&self.expr));
-
-        [email, length, url].into_iter().flatten().collect()
+        self.validations
+            .iter()
+            .filter(|validation| !validation.is_async())
+            .map(|validation| validation.tokens(&self.expr))
+            .collect()
     }
 
     pub fn async_validations(&self) -> Vec<TokenStream> {
-        vec![]
+        self.validations
+            .iter()
+            .filter(|validation| validation.is_async())
+            .map(|validation| validation.tokens(&self.expr))
+            .collect()
     }
 }
diff --git a/packages/fortifier-macros/src/validation.rs b/packages/fortifier-macros/src/validation.rs
new file mode 100644
index 0000000..b52c705
--- /dev/null
+++ b/packages/fortifier-macros/src/validation.rs
@@ -0,0 +1,14 @@
+use proc_macro2::TokenStream;
+use syn::{Result, meta::ParseNestedMeta};
+
+pub trait Validation {
+    fn parse(_meta: &ParseNestedMeta<'_>) -> Result<Self>
+    where
+        Self: Sized;
+
+    fn is_async(&self) -> bool;
+
+    fn error_type(&self) -> TokenStream;
+
+    fn tokens(&self, expr: &TokenStream) -> TokenStream;
+}
diff --git a/packages/fortifier-macros/src/validations/email.rs b/packages/fortifier-macros/src/validations/email.rs
index 47c476d..fd95f67 100644
--- a/packages/fortifier-macros/src/validations/email.rs
+++ b/packages/fortifier-macros/src/validations/email.rs
@@ -2,15 +2,25 @@ use proc_macro2::TokenStream;
 use quote::quote;
 use syn::{Result, meta::ParseNestedMeta};
 
+use crate::validation::Validation;
+
 #[derive(Default)]
 pub struct Email {}
 
-impl Email {
-    pub fn parse(_meta: &ParseNestedMeta<'_>) -> Result<Email> {
+impl Validation for Email {
+    fn parse(_meta: &ParseNestedMeta<'_>) -> Result<Self> {
         Ok(Email::default())
     }
 
-    pub fn tokens(&self, expr: &TokenStream) -> TokenStream {
+    fn is_async(&self) -> bool {
+        false
+    }
+
+    fn error_type(&self) -> TokenStream {
+        quote!(EmailError)
+    }
+
+    fn tokens(&self, expr: &TokenStream) -> TokenStream {
         quote! {
             #expr.validate_email()
         }
diff --git a/packages/fortifier-macros/src/validations/length.rs b/packages/fortifier-macros/src/validations/length.rs
index 5799e68..6883db9 100644
--- a/packages/fortifier-macros/src/validations/length.rs
+++ b/packages/fortifier-macros/src/validations/length.rs
@@ -2,6 +2,8 @@ use proc_macro2::TokenStream;
 use quote::quote;
 use syn::{Expr, Result, meta::ParseNestedMeta};
 
+use crate::validation::Validation;
+
 #[derive(Default)]
 pub struct Length {
     pub equal: Option<Expr>,
@@ -9,8 +11,8 @@ pub struct Length {
     pub max: Option<Expr>,
 }
 
-impl Length {
-    pub fn parse(meta: &ParseNestedMeta<'_>) -> Result<Length> {
+impl Validation for Length {
+    fn parse(meta: &ParseNestedMeta<'_>) -> Result<Self> {
         let mut result = Length::default();
 
         meta.parse_nested_meta(|meta| {
@@ -37,7 +39,15 @@ impl Length {
         Ok(result)
     }
 
-    pub fn tokens(&self, expr: &TokenStream) -> TokenStream {
+    fn is_async(&self) -> bool {
+        false
+    }
+
+    fn error_type(&self) -> TokenStream {
+        quote!(LengthError<usize>)
+    }
+
+    fn tokens(&self, expr: &TokenStream) -> TokenStream {
         let equal = if let Some(equal) = &self.equal {
             quote!(Some(#equal))
         } else {
diff --git a/packages/fortifier-macros/src/validations/url.rs b/packages/fortifier-macros/src/validations/url.rs
index 290b84e..093cbbe 100644
--- a/packages/fortifier-macros/src/validations/url.rs
+++ b/packages/fortifier-macros/src/validations/url.rs
@@ -2,15 +2,25 @@ use proc_macro2::TokenStream;
 use quote::quote;
 use syn::{Result, meta::ParseNestedMeta};
 
+use crate::validation::Validation;
+
 #[derive(Default)]
 pub struct Url {}
 
-impl Url {
-    pub fn parse(_meta: &ParseNestedMeta<'_>) -> Result<Url> {
+impl Validation for Url {
+    fn parse(_meta: &ParseNestedMeta<'_>) -> Result<Self> {
         Ok(Url::default())
     }
 
-    pub fn tokens(&self, expr: &TokenStream) -> TokenStream {
+    fn is_async(&self) -> bool {
+        false
+    }
+
+    fn error_type(&self) -> TokenStream {
+        quote!(UrlError)
+    }
+
+    fn tokens(&self, expr: &TokenStream) -> TokenStream {
         quote! {
             #expr.validate_url()
         }