Component API
=============
The component API is used to access and interact with components available to a computer. Also see [[:component:component_access|the page on component interaction]].

- `component.doc(address:string, method:string): string`  
  Returns the documentation string for the method with the specified name of the component with the specified address, if any. Note that you can also get this string by using `tostring` on a method in a proxy, for example `tostring(component.screen.isOn)`.
- `component.invoke(address:string, method:string[, ...]): ...`  
  Calls the method with the specified name on the component with the specified address, passing the remaining arguments as arguments to that method. Returns the result of the method call, i.e. the values returned by the method. Depending on the called method's implementation this may throw.
- `component.list([filter:string[, exact:boolean]]):function`  
  Returns a table with all components currently attached to the computer, with address as a key and component type as a value. It also provides iterator syntax via `__call`, so you can use it like so: `for address, componentType in component.list() do ... end`  
  If `filter` is set this will only return components that contain the filter string (this is *not* a pattern/regular expression). For example, `component.list("red")` will return `redstone` components.  
  If `true` is passed as a second parameter, exact matching is enforced, e.g. `red` will *not* match `redstone`.
- `component.methods(address:string):table`  
  Returns a table with the names of all methods provided by the component with the specified address. The names are the keys in the table, the values indicate whether the method is called directly or not.
- `component.proxy(address:string):table`  
  Gets a 'proxy' object for a component that provides all methods the component provides as fields, so they can be called more directly (instead of via `invoke`). This is what's used to generate 'primaries' of the individual component types, i.e. what you get via `component.blah`.  
  For example, you can use it like so: `component.proxy(component.list("redstone")()).getInput(sides.north)`, which gets you a proxy for the first `redstone` component returned by the `component.list` iterator, and then calls `getInput` on it.  
  Note that proxies will always have at least two fields, `type` with the component's type name, and `address` with the component's address.
- `component.type(address:string):string`  
  Get the component type of the component with the specified address.
- `component.slot(address:string):string`  
  Return slot number which the component is installed into. Returns -1 if it doesn't otherwise make sense.
- `component.fields(address:string):string`  
  Undocumented
- `component.get(address: string[, componentType: string]): string | (nil, string)`  
  Tries to resolve an abbreviated address to a full address. Returns the full address on success, or `nil` and an error message otherwise. Optionally filters by component type.
- `component.isAvailable(componentType: string): boolean`  
  Checks if there is a primary component of the specified component type.
- `component.getPrimary(componentType: string): table`  
  Gets the proxy for the primary component of the specified type. Throws an error if there is no primary component of the specified type.
- `component.setPrimary(componentType: string, address: string)`  
  Sets a new primary component for the specified component type. The address may be abbreviated, but must be valid if it is not `nil`. Triggers the `component_unavailable` and `component_available` signals if set to `nil` or a new value, respectively.
  
Note that the component API has a metatable that allows the following syntax:

```lua
local component = require("component")
local rs0 = component.getPrimary("redstone")
local rs1 = component.redstone -- syntactic sugar
print(rs0 == rs1) -- true
```


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