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Replace spread operator with eval() to allow safe transpilation to ES5 #4

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Replace spread operator with eval() to allow safe transpilation to ES5 #4

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7 changes: 5 additions & 2 deletions src/runtime.js
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Original file line number Diff line number Diff line change
@@ -1,10 +1,13 @@
// You can store this to call your function. this must be bound to the current instance.
export function SuperCall(selector, argTypes, returnType) {
const func = CFunc("objc_msgSendSuper", [{type: '^' + objc_super_typeEncoding}, {type: ":"}, ...argTypes], returnType);
return function(...args) {
return function() {
const struct = make_objc_super(this, this.superclass());
const structPtr = MOPointer.alloc().initWithValue_(struct);
return func(structPtr, selector, ...args);
const params = ['structPtr', 'selector'].concat(
[].slice.apply(arguments).map((val, i) => `arguments[${i}]`)
)
return eval(`func(${params.join(', ')})`)
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so this is supposed to yield a string like func(structPtr, selector, arguments[0], arguments[1], arguments[2]), right?

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@darknoon darknoon Sep 15, 2017 •
edited
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would something like this work?

return func.apply(undefined, [structPtr, selector, ...arguments])

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Sorry for the delay. That'd work in a normal JavaScript environment -- in fact that's pretty much how babel transforms the spread operator iirc. But it won't work in CocoaScript as the MOBridgeSupportFunction returned by CFunc doesn't support .apply() (apply is undefined).

The eval() I'm using here is really just a poor-mans .apply() to pass all the supplied arguments on to the MOBridgeSupportFunction invocation. There may be a better way to do it though?

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@kannonboy would it work to grab apply from somewhere else and then call it with a MOBridgeSupportFunction?. eval is a pretty bad hack from a perf and cleanliness perspective. Overall this library has some nasty hacks on the objc side, so I guess we can use it if all else fails.

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@darknoon I agree using eval() it's pretty far from ideal, but I think it might be the best option available.

I tried to see if I could repurpose Function.prototype.apply() by messing around in Sketch's console, but it doesn't quite work as I'd hoped:

Function.prototype.apply.apply(
  function(arg) {
    log('called with ' + arg)
  },
  ['cat']
)

Result is:

called with undefined

And the implementation of .apply() is native of course (you can test with log(Function.prototype.apply.toString()))

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Performance wise is slice bad for arguments and eval bad for variable lookup etc. See #8 for more + tested alternative solution :)

};
}

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