Get each char (with shape) of font from UIFont or .ttf file

Question

I have not exact idea for it is possible or not and also I did try to find solution for my question but did't get success, that's why I am asking here and hope that I will get solution.

I am developing one drawing related app in which I want to get shape of each font that provided by .ttf file or UIFont.

For Ex.

If I have UIFont/.ttf file such like "OpenSans-Italic" then how can get each "char" with it's shape (here "Italic" shape) of "OpenSans" font? And I want to this in Char or NSString.

=> @[ @"a", @"b", @"c", @"d",..@"A", @"B", @"C", @"D",.....@"1", @"2", @"3"....]; // This is char array only for understanding purpose.

Please suggest me, how can I get this?