Prototype Your Commands and Their Handlers

Prototype Your Commands and Their Handlers

Tutorial VLF004 - Prototyping Your Commands

Command

Command Handler

Mock Up Filters and Command Handlers

Then create command handlers for your application and business objects. Use the prototype command handlers or create your own mock-up command handlers. You don't yet write any code.

Some Guidelines for Defining Commands

• Many commands are verbs and some are nouns. Most of the noun commands actually have an implied verb associated with them (e.g.: the command "Picture" is actually "Show me a Picture").

 

• If commands are actually verbs (real or implied) then you should try to always think about defining commands in the Object –> Action context:   The user first chooses the Object (i.e.: the Framework, an application or a business object), then they indicate the Action they would like to take on the object by selecting a command.

 

• This is different to the way that many procedural menu based systems work. Classically they are Action –> Object orientated.

 

• You should try to use simple, reusable and generic nouns or verbs for commands. 

 

• For example, use "Details" rather then "Customer Details" as this will allow the command "Details" to be reused with many other objects such as Employees, Products and Orders … saving you from overcrowding your Framework with "Employee Details", "Product Details" and "Order Details". 

 

• Users will understand the command "Details" applies to the currently selected object (e.g.: Customer, Order, Employee or Product) for the same reason that they understand that "Copy" in MS-PowerPoint means to copy the currently selected object ..… which is why MS-PowerPoint does not have to have "Copy Text", "Copy Picture", "Copy Clip-Art", etc and can have a single "Copy" reusable command.