3 files changed, 18 insertions, 21 deletions
diff --git a/activemodel/lib/active_model/callbacks.rb b/activemodel/lib/active_model/callbacks.rb
index 16188aec6b..8b09f8b203 100644
--- a/activemodel/lib/active_model/callbacks.rb
+++ b/activemodel/lib/active_model/callbacks.rb
@@ -100,7 +100,7 @@ module ActiveModel
     def define_model_callbacks(*callbacks)
       options = callbacks.extract_options!
       options = {
-        terminator: "result == false",
+        terminator: ->(_,result) { result == false },
         skip_after_callbacks_if_terminated: true,
         scope: [:kind, :name],
         only: [:before, :around, :after]
@@ -120,30 +120,24 @@ module ActiveModel
     private
 
     def _define_before_model_callback(klass, callback) #:nodoc:
-      klass.class_eval <<-CALLBACK, __FILE__, __LINE__ + 1
-        def self.before_#{callback}(*args, &block)
-          set_callback(:#{callback}, :before, *args, &block)
-        end
-      CALLBACK
+      klass.define_singleton_method("before_#{callback}") do |*args, &block|
+        set_callback(:"#{callback}", :before, *args, &block)
+      end
     end
 
     def _define_around_model_callback(klass, callback) #:nodoc:
-      klass.class_eval <<-CALLBACK, __FILE__, __LINE__ + 1
-        def self.around_#{callback}(*args, &block)
-          set_callback(:#{callback}, :around, *args, &block)
-        end
-      CALLBACK
+      klass.define_singleton_method("around_#{callback}") do |*args, &block|
+        set_callback(:"#{callback}", :around, *args, &block)
+      end
     end
 
     def _define_after_model_callback(klass, callback) #:nodoc:
-      klass.class_eval <<-CALLBACK, __FILE__, __LINE__ + 1
-        def self.after_#{callback}(*args, &block)
-          options = args.extract_options!
-          options[:prepend] = true
-          options[:if] = Array(options[:if]) << "value != false"
-          set_callback(:#{callback}, :after, *(args << options), &block)
-        end
-      CALLBACK
+      klass.define_singleton_method("after_#{callback}") do |*args, &block|
+        options = args.extract_options!
+        options[:prepend] = true
+        options[:if] = Array(options[:if]) << "value != false"
+        set_callback(:"#{callback}", :after, *(args << options), &block)
+      end
     end
   end
 end
diff --git a/activemodel/lib/active_model/lint.rb b/activemodel/lib/active_model/lint.rb
index 1be2913f0b..46b446dc08 100644
--- a/activemodel/lib/active_model/lint.rb
+++ b/activemodel/lib/active_model/lint.rb
@@ -98,7 +98,7 @@ module ActiveModel
 
       private
         def model
-          assert @model.respond_to?(:to_model), "The object should respond_to to_model"
+          assert @model.respond_to?(:to_model), "The object should respond to to_model"
           @model.to_model
         end
 
diff --git a/activemodel/lib/active_model/validations/callbacks.rb b/activemodel/lib/active_model/validations/callbacks.rb
index 8de36b4f8b..cabb9482f2 100644
--- a/activemodel/lib/active_model/validations/callbacks.rb
+++ b/activemodel/lib/active_model/validations/callbacks.rb
@@ -22,7 +22,10 @@ module ActiveModel
 
       included do
         include ActiveSupport::Callbacks
-        define_callbacks :validation, terminator: "result == false", skip_after_callbacks_if_terminated: true, scope: [:kind, :name]
+        define_callbacks :validation,
+                         terminator: ->(_,result) { result == false },
+                         skip_after_callbacks_if_terminated: true,
+                         scope: [:kind, :name]
       end
 
       module ClassMethods