objc block take the responsibility in current scope

block.m

typedef NSString* (^ConfigureNameBlock)(NSString *firstName, NSString *lastName);

- (void) runBlock
{
    NSString *suffix = @"i am in your back";
    
    NSString *(^configureName)(NSString *, NSString *) = ^(NSString *firstName, NSString *lastName) {
        return [NSString stringWithFormat: @"%@, %@, %@", firstName, lastName, suffix];
    };
    
    NSLog(@"%@", [self displayName:@"peter" configureName:configureName]);
    // => peter, is the best of the world, i am in your back
}

- (NSString *)displayName: (NSString *) firstName
            configureName: (ConfigureNameBlock) aConfigureBlock
            // configureName: (NSString *(^)(NSString *firstName, NSString *lastName)) aConfigureBlock
{
        
    return aConfigureBlock(firstName, @"is the best of the world");
}