Advice how to present calculation of #records

Question

I have an app that have a lot of records that i am loading into a core data DB. The actual loading is done in a module called "loadDBRecords". This module is called from "MainViewController", which is connected to "MainViewController.xib".

As the loading takes quite some time i have added an UIActivityIndicatorView to the .xib during the load. However, i would like to use a UIProgressView. When i look at this i do not see any way of using that unless i move the loading code from "loadDBRecords" to the "MainViewController".

My question is: What is the best way of leveraging the UIProgressView with my setup?

Answer 1

You could add a "progressHandler" block to the -loadDBRecords method. Execute the block for every record you load, and pass back a floating-point value between 0.0 and 1.0 indicating the progress thus far. The block can then assign that value to the progress bar, or print it to the console, or whatever you need it to do. (Traditionally, this would be done with a function pointer or a delegate/selector combination, but I've found blocks tend to make your intent clearer—or at least make it easier to show your intent.)

- (void)loadDBRecords:(void (^)(CGFloat progress))progressHandler {
    NSUInteger count = /* number of records*/;
    for (NSUInteger i = 0; i < count; i++) {
        /* load the record */
        progressHandler((CGFloat)n / (CGFloat)count);
    }
}