added action

app/controllers/admin/accounts_controller.rb

@@ -16,12 +16,12 @@ module Admin
 
     def update
       if @account.valid?
-        @sum = params[:account][:balance].to_f - @account.balance
-        action = Actions::AccountActivityCreate.new(@account, @sum, params[:description],
-                                                    AccountActivity::UPDATE_CREDIT)
-        redirect_to admin_accounts_path, notice: t('.updated') if action.call
+        action = Actions::AccountActivityCreate.new(@account, params[:account][:balance],
+                                                    params[:description], AccountActivity::UPDATE_CREDIT)
+        redirect_to admin_accounts_path, notice: t('.updated') and return if action.call
       end
 
+      flash[:alert] = t('invalid_balance')
       render 'edit'
     end
 

app/interactions/actions/account_activity_create.rb

@@ -1,17 +1,35 @@
 module Actions
   class AccountActivityCreate
-    def initialize(account, sum, description, type)
+    def initialize(account, new_balance, description, type)
       @account = account
-      @sum = sum
+      @new_balance = new_balance
       @description = description
       @type = type
     end
 
     def call
+      validate_new_balance
+      return false if @error
+
+      calc_sum
       create_activity
       commit
     end
 
+    def calc_sum
+      @sum = @new_balance.to_f - @account.balance
+    end
+
+    def validate_new_balance
+      return if @new_balance.blank?
+
+      begin
+        !Float(@new_balance).nil?
+      rescue StandardError
+        @error = true
+      end
+    end
+
     def create_activity
       @activity = AccountActivity.new(account: @account,
                                       sum: @sum,

config/locales/admin/accounts.en.yml

@@ -1,5 +1,7 @@
 en:
   edit_balance: Edit balance
+  invalid_balance: The balance must be a number
+
   admin:
     accounts:
       index: