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Objective-C (Wasm)

Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to C.

In LiveCodes, Objective-C runs in the browser using Clang compiled to WebAssembly, with GNUstep's libobjc2 as the Objective-C runtime.

Usage​

Demo:

show code
import { createPlayground } from 'livecodes';

const options = {
  "config": {
    "activeEditor": "script",
    "script": {
      "language": "objc-wasm",
      "content": "#import <stdio.h>\n#import <objc/runtime.h>\n\n__attribute__((objc_root_class))\n@interface Greeter {\n    Class isa;\n}\n- (void)greet:(const char *)name;\n@end\n\n@implementation Greeter\n- (void)greet:(const char *)name {\n    printf(\"Hello, %s!\\n\", name);\n}\n@end\n\nint main(void) {\n    Greeter *greeter = class_createInstance(objc_getClass(\"Greeter\"), 0);\n    [greeter greet:\"World\"];\n    return 0;\n}"
    },
    "mode": "simple",
    "editor": "auto",
    "tools": {
      "status": "full"
    }
  }
};
createPlayground('#container', options);

Communication with JavaScript​

The Objective-C code runs in the context of the result page. A few helper properties and methods are available in the browser global livecodes.objc object:

  • livecodes.objc.input: The initial standard input passed to the code.
  • livecodes.objc.loaded: A promise that resolves when the environment is fully loaded. Other helpers should be used after this promise resolves.
  • livecodes.objc.output: The standard output from the code execution.
  • livecodes.objc.error: The compiler diagnostics, if the code failed to compile.
  • livecodes.objc.exitCode: The exit code of the program.
  • livecodes.objc.run: A function that compiles and runs the code with new input. This function takes a string as input and returns a promise that resolves with an object containing the output, error and exitCode properties.

Example:

show code
import { createPlayground } from 'livecodes';

const options = {
  "template": "objc-wasm",
  "params": {
    "activeEditor": "markup"
  }
};
createPlayground('#container', options);

The same API is available as livecodes.clangWasm for all Clang-based languages.

Language Info​

Name​

objc-wasm

Aliases / Extensions​

m, objc, objc-wasm, objective-c, wasm.m, clang.m, clang-objc

Editor​

script

Compiler​

Clang compiled to WebAssembly via @live-codes/clang-wasm, with a complete libc.

Version​

Clang v22.1.8. The standards gnu11, gnu17 and gnu23 are supported (default: gnu23).

Limitations​

The Objective-C runtime is GNUstep's libobjc2, which is a runtime and not a class library. There is no NSObject and no NSString, and Foundation is not available. Programs declare their own root class (as in the example above) and create instances directly.

Objective-C exceptions (@try/@catch/@throw) are not supported.

Custom Settings​

The Clang compiler can be configured using custom settings added to the property objc-wasm:

PropertyTypeDescription
stdstringThe Objective-C standard to compile with: gnu11, gnu17 or gnu23. Defaults to gnu23.
compileArgsstring[]Extra clang flags, e.g. ["-Wall", "-O2"].
argsstring[]Command-line arguments passed to the program (argv).
Custom Settings
{
  "objc-wasm": {
    "std": "gnu17",
    "compileArgs": ["-Wall", "-O2"],
    "args": ["--name", "LiveCodes"]
  }
}

Code Formatting​

Using @wasm-fmt/clang-format, applying Google's C++ style guide.

Live Reload​

By default, new code changes are sent to the result page without a full page reload, avoiding the need to re-download the compiler. This behavior can be disabled by adding the code comment // __livecodes_reload__ to the code, which forces a full page reload.

This comment can be added in the hiddenContent property of the editor for embedded playgrounds.

Example Usage​

#import <stdio.h>
#import <objc/runtime.h>

__attribute__((objc_root_class))
@interface Greeter {
    Class isa;
}
- (void)greet:(const char *)name;
@end

@implementation Greeter
- (void)greet:(const char *)name {
    printf("Hello, %s!\n", name);
}
@end

int main(void) {
    Greeter *greeter = class_createInstance(objc_getClass("Greeter"), 0);
    [greeter greet:"LiveCodes"];
    return 0;
}

Starter Template​

https://livecodes.io/?template=objc-wasm

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