Executing code defined in a string

Question

I would like to be able to execute a piece of code that is defined in a string. I am aware of performSelector: but the object that will perform the selector is going to be different.

Example strings

[[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo] hasFlash]
[UIImagePickerController isCameraDeviceAvailable:UIImagePickerControllerCameraDeviceFront]

So what I would like to do is something along the lines of

SEL selector = NSSelectorFromString(@"[[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo] hasFlash]");
if (selector) {
    // Show flash buttons
}

Sorry, not possible: stackoverflow.com/questions/10158036/eval-in-objective-c — fguchelaar
– fguchelaar, Commented Mar 1, 2013 at 10:50
Just think of it for a while: Isn't objective-c a compiled language? Does your phone have a compiler for this? Let's think about this a bit more: wouldn't this create a security issue? — ppeterka
– ppeterka, Commented Mar 1, 2013 at 10:50

Anoop Vaidya · Accepted Answer · 2013-03-01 10:51:42Z

2

You can not fire a selector that calls a nested method call.

Selectors are only method names with showing number of arguments as method:abc:yxa:

As the statement below:

SEL selector = NSSelectorFromString(@"[[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo] hasFlash]");

is calling

[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]

then

[objectReturnedByAbove hasFlash]

answered Mar 1, 2013 at 10:51

Anoop Vaidya

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2 Comments

user2123173 Over a year ago

I understand. I would be able to by breaking down the strings but then there are better solutions for this problem. Thanks!

Anoop Vaidya Over a year ago

few weeks ago, i need similar kind of thing, i posted and got a lot downvotes and question got removed. You should thank to everyone as your question is still here :D

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