Convert NSString to 4 by 4 float Matrix

Question

I was wondering if there is a convenience method or something to change a NSString to an array of floats, for example.

I have a string which reads like this:

{{-0.528196, -0.567599, -0.631538, 0}, {0.0786662, -0.773265, 0.629184, 0}, {-0.845471, 0.282651, 0.453086, 0}, {0, 0, 0, 1}}

Which I got by the method:

NSStringFromGLKMatrix4()

And i want to do this:

float test[4][4] = {{-0.528196, -0.567599, -0.631538, 0}, {0.0786662, -0.773265, 0.629184, 0}, {-0.845471, 0.282651, 0.453086, 0}, {0, 0, 0, 1}};

return GLKMatrix4MakeWithArray(*test);

Any help will be appreciated, thanks.

Answer 1

This is kinda ugly, but it should work:

// your string data
NSString* s = @"{{-0.528196, -0.567599, -0.631538, 0}, {0.0786662, -0.773265, 0.629184, 0}, {-0.845471, 0.282651, 0.453086, 0}, {0, 0, 0, 1}}";

// remove uneccessary characters from string.. 
s = [s stringByReplacingOccurrencesOfString:@"{" withString:@""];
s = [s stringByReplacingOccurrencesOfString:@"}" withString:@""];
s = [s stringByReplacingOccurrencesOfString:@" " withString:@""];

// build an NSArray with string components and convert them to an array of floats
NSArray* array = [s componentsSeparatedByString:@","];
float data[16];
for(int i = 0; i < 16; ++i){
    data[i] = [[array objectAtIndex:i] floatValue];
}

GLKMatrix4 matrix = GLKMatrix4MakeWithArray(data);

If you're targeting iOS 4.0 or higher, you might also use NSRegularExpression to get the numbers out of the string.