On-demand Texture Loading with GLKit - iphone

Question

I have an application in which I need to draw text on the screen using OpenGL textures. In my render loop I request the textures from my TextureController, which has functions such as
- (GLuint)textureForImageNamed:(NSString*)fileName;
{
// we're checking a hash.. possibly slow
NSNumber* textureHandle = [textures objectForKey:fileName];
if(!textureHandle)
textureHandle = [self loadTexture:fileName];
GLuint handle = (GLuint)[textureHandle unsignedIntValue];
return handle;
}
where loadTexture loads the texture into memory like this
- (NSNumber*)loadTexture:(NSString*)fileName
{
GLuint texID = [GLKTextureLoader textureWithCGImage:
[[UIImage imageNamed:#"star.png"] CGImage]
options:nil
error:nil].name;
NSNumber* num = [NSNumber numberWithUnsignedInt:texID];
[textures setObject:num forKey:fileName];
return num;
}
And similar functions for text:
- (GLuint)textureForTextWithString:(NSString*)text;
- (NSNumber*)loadTextureForString:(NSString*)text;
This all works fine when I have requested the image once before my render loop, but the whole point is that the text and images that need to be drawn are not known in advance. So I want to be able to call textureForTextWithString:#"fooBar" and either give me the texture if it was loaded before, or load it in -- add it to the dictionary and then give it to me. However, I get a black texture for all the textures that weren't preloaded (i.e. for which textureForTextWithString:#"fooBar" was not called before I started the render loop).
Relevant code in the render loop:
GLuint secondTex = [textures textureForTextWithString:#"NO"];
glBindTexture(GL_TEXTURE_2D, secondTex);
glBindBuffer(GL_ARRAY_BUFFER, some_vertex_buffer);
glDrawArrays(GL_POINTS, 0, num);
I am looking for a solution, or better yet -- advice on how to better handle this particular problem.
EDIT: The two files in question can be found here:
https://gist.github.com/3153940 - The main OpenGL VC
https://gist.github.com/3153941 - The texture controller