Velcro

Basic introduction

Velcro is a lightweight Nim ECS library for runtime-attached components.

The two modes

Default

By default, your parent objects need to have a velcro field with the type of VelcroObj. Components need to inherit from VelcroComp. You can attach and detach these with add and delete. The parent object and the component can have any other field, as they don't influence the workings of the library. You can check whether an object has a specific component through has, where you pass the object and the component's typedesc. To access a component, you can index it: yourVelcroObj[YourVelcroComp] - Note: You index an initialized value with the type's name.

ECS

To enable this mode, you have two options: - Through a compiler flag: -d:velcroOwned - Through a pragma: {.define:velcroOwned.}

This changes how the library handles data, so now your parent objects have to inherit from VelcroObj. Components work the same. You can still attach and detach with add and delete. To have your objects in the database, you have to upload them using upload. To query the DB, you can use - querySet, which works with any number of values but returns a HashSet - If there are multiple values, the sets are intersected - query, which converts the HashSet to a seq, but only works with a single input - or querySetAny, which is similar to querySet, but unionizes the values instead.

Queries return a VelcroHandler, which can be used the same as the actual object. - Note: You can't access the actual object's fields after you have uploaded it, only the original variable can.