Lua-Objective-C-Bridge

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Lua-Objective-C-Bridge

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Bridge between Lua and Objective-C which allows you to call a Objective-C method from a Lua script using NSInvocation.

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Lua-Objective-C Bridge
======================

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Synopsis
--------

local ctx = objc.context:create()
    local img = ctx:wrap(objc.class.UIImage)("imageNamed:", "spaceship.png")
    local ship = ctx:wrap(objc.class.UIImageView)("alloc")("initWithImage:", -img)

The Lua code above is equivalent to following Objective-C code:

UIImage *img = [UIImage imageNamed:@"spaceship.png"];
    UIImageView *ship = [[UIImageView alloc] initWithImage:img];

More Example:
https://github.com/torus/ios-lua-lander/blob/master/LuaLander/LuaLander/bootstrap.lua

Requirements
------------

-   Lua 5.2.x or Lua 5.3.x
-   iOS 8.0 or later (probably works on older iOS)
-   or macOS 10.13 or later (probably works on older macOS)

Usage
-----

Just add following files to your project:

-   LuaBridge.h
-   LuaBridge.m
-   LuaBridgeInternal.h
-   utils.lua
-   Lua source code (excluding lua.c and luac.c)

Samples/Tests
-------------

Please see LuaObjCBridge and LuaObjCBridgeMac projects.

Objective-C API
---------------

First, import Lua and the bridge header files:

#import "lua.h"
    #import "lualib.h"
    #import "lauxlib.h"
    #import "LuaBridge.h"

Then,

lua_State *L = [[LuaBridge instance] L];

gets the lua_State object to call Lua functions.

High-Level Lua API
------------------

local ctx = objc.context:create()

Creates a new context.

local wrapped_object = ctx:wrap(...)

Returns wrapped Objective-C object. Then, you can send a message to the object like:

wrapped_object("setOpaque:", false)

You need to unwrap the object to pass to a method using `-` (unary minus) like:

local webview = ctx:wrap(objc.class.UIWebView)("alloc")("initWithFrame:", -rect)

Any Objective-C class object can be obtained via `objc.class` table. For example

objc.class.UIWebView

Returns the UIWebView class object.

Extending the Bridge
--------------------

LuaBridge uses a stack to share objects between Lua and Objective-C.
And some operators are defined to handle stuff in the stack.

You can add user-defined operators to the LuaBridge class folloing this signature:

- (void)op_your_operator:(NSMutableArray*)stack

Low-Level Lua API
-----------------

### newstack

stack = objc.newstack()

Returns a new stack to pass and receive paramters between Lua and Objective-C.

### push

objc.push(stack, arg, ...)

Pushes one or more arguments to the stack.

### pop

val = objc.pop(stack)

Pops the last (top) value from the stack.

### operate

objc.operate(stack, "operator_name")

Calls given operator with the content of the stack.

### getclass

cls = objc.getclass(class_name)

Returns the class object for given class name.

Data Type Conversion
---------------

<table>
<tr><th>Lua</th><th>Objective-C</th></tr>
<tr><td>nil</td><td>NSNull (nil)</td></tr>
<tr><td>string</td><td>NSString</td></tr>
<tr><td>number, boolean</td><td>NSNumber</td></tr>
<tr><td>userdata</td><td>other NSObject-derived type</td></tr>
<tr><td>lightuserdata</td><td>void *</td></tr>
<tr><td>table, function, thread</td><td>LuaObjectReference</td></tr>
</table>

Pre-defined Operators
---------------------

### call

objc.push(stack, ..., arg2, arg1, target, selector)
    objc.operate(stack, "call")
    local ret = objc.pop(stack)

"call" operator sends a method specified by selector to the target, then pushes the returned object.
Please note that the argments must be pushed in reverse order.
This is equivalent to following Objective-C expression:

ret = [target selector arg1 arg2 ...]

Adding Operators
----------------

Create a category on the LuaBrige class and implement your operators in folloing signature:

- (void)op_your_operator:(NSMutableArray*)stack

Then from Lua script call the operator like this:

objc.operate(stack, "your_operator")

Note that in Objective-C, the method name should be "op_*your_operator*:".

License
=======
The MIT License (MIT)

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

Author
======
Toru Hisai toru@torus.jp @torus

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