How to split lengthy uiviewcontroller class? - ios

Question

I have a long UIViewController with lots of sections and rows. In spite of having separate methods for each of these sections, it still becomes cumbersome jumping to different methods. Is there a best way to design such class? I was thinking of having a category for each of these sections? is it a good idea?

Answer 1

I've found that code related to delegate methods become a large part of my view controllers. One strategy, described in this article at objc.io, is to move data source delegate methods to their own class.

Answer 2

In the last year I started to move out as much code as possible from my view controllers, attempting to create «Lighter View Controllers». There-for you can use objects that implement one — and only one — certain aspect of the functionality that the view controller will have. You could call it Sub Controller, but I and others use the name «Intentions» to express the fact, that each of this objects has one intention.
I experimented with different kinds, from target/action to block based, that I finally found to be the most useful.
An example from real code:
I habe a cash register app that need to communicate via wifi with thermal printers.
To add a printer I have the AddPrinterViewController with textfields for ip address, port and name/location.
Instead of implementing the view controller as delegate for all the textfields I create on class that will serve as delegate for one textfield and has a block-based validation.
#interface TextfieldDelegateIntention : NSObject
#property(nonatomic, weak, readonly) UITextField *textField;
#property (nonatomic, copy) BOOL (^validationBlock)(UITextField *textField);
-(instancetype)initWithTextField:(UITextField *)textField
validationBlock: (BOOL (^)(UITextField *textField)) validationBlock;
-(BOOL)validate;
#end
#import "TextfieldDelegateIntention.h"
#interface TextfieldDelegateIntention ()<UITextFieldDelegate>
#property(nonatomic, weak) UITextField *textField;
#end
#implementation TextfieldDelegateIntention
-(instancetype)initWithTextField:(UITextField *)textField
validationBlock: (BOOL (^)(UITextField *textField)) validationBlock
{
self = [super init];
if(self){
self.validationBlock = validationBlock;
self.textField = textField;
self.textField.delegate = self;
}
return self;
}
-(BOOL)validate
{
if (self.validationBlock) {
return self.validationBlock(self.textField);
}
return NO;
}
-(BOOL)textFieldShouldReturn:(UITextField *)textField
{
[textField resignFirstResponder];
return YES;
}
-(void)textFieldDidEndEditing:(UITextField *)textField
{
[textField resignFirstResponder];
}
#end
I setup the view controller with the three textfields in the storyboard.
The IP (version 4 only) address' textfield could look like this:
TextfieldDelegateIntention *ipAddresIntention = [[TextfieldDelegateIntention alloc] initWithTextField:self.ipTextField validationBlock:^BOOL(UITextField *textField) {
NSArray *components = [textField.text componentsSeparatedByString:#"."];
if ([components count] == 4) {
__block BOOL compsAreValidNumbers = YES;
[components enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if ([obj integerValue] > -1 && [obj integerValue] < 256 ) {
} else {
compsAreValidNumbers = NO;
*stop = YES;
}
}];
return compsAreValidNumbers;
}
return NO;
}];
A overly simple validation, but useful to assist the user with the correct input.
The complete view controller's code looks like
#import <UIKit/UIKit.h>
#import "BaseModalViewController.h"
#class NamendPOSNetworkPrinter;
#class PrinterProvider;
#interface AddPrinterViewController : BaseModalViewController
#property (nonatomic, strong) PrinterProvider *printerProvider;
#property (nonatomic, copy) void(^printerPreferecesEntered)(NSDictionary *printerDict);
#end
#import "AddPrinterViewController.h"
#import "TextfieldDelegateIntention.h"
#import "ButtonIntention.h"
#import "PrinterProvider.h"
#interface AddPrinterViewController ()
#property (weak, nonatomic) IBOutlet UITextField *nameTextField;
#property (weak, nonatomic) IBOutlet UITextField *ipTextField;
#property (weak, nonatomic) IBOutlet UITextField *portTextField;
#property (nonatomic, strong) NSArray *textFieldIntentions;
#property (nonatomic, strong) ButtonIntention *okIntention;
#property (weak, nonatomic) IBOutlet UIButton *okButton;
#end
#implementation AddPrinterViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
TextfieldDelegateIntention *nameIntention = [[TextfieldDelegateIntention alloc] initWithTextField:self.nameTextField validationBlock:^BOOL(UITextField *textField) {
if ([textField.text length] > 0) {
return YES;
}
return NO;
}];
TextfieldDelegateIntention *ipAddresIntention = [[TextfieldDelegateIntention alloc] initWithTextField:self.ipTextField validationBlock:^BOOL(UITextField *textField) {
NSArray *components = [textField.text componentsSeparatedByString:#"."];
if ([components count] == 4) {
__block BOOL compsAreValidNumbers = YES;
[components enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if ([obj integerValue] > -1 && [obj integerValue] < 256 ) {
} else {
compsAreValidNumbers = NO;
*stop = YES;
}
}];
return compsAreValidNumbers;
}
return NO;
}];
TextfieldDelegateIntention *portIntention = [[TextfieldDelegateIntention alloc] initWithTextField:self.portTextField validationBlock:^BOOL(UITextField *textField) {
if ([textField.text integerValue] > 1023 && [textField.text integerValue]< 65536) {
return YES;
}
return NO;
}];
self.textFieldIntentions = #[nameIntention, ipAddresIntention, portIntention];
__block typeof(self) weakSelf = self;
ButtonIntention *okIntention = [[ButtonIntention alloc] initWithButton:self.okButton actionBlock:^(UIButton *button) {
typeof(weakSelf) strongSelf = weakSelf;
if (strongSelf) {
__block BOOL formIsValid = YES;
[strongSelf.textFieldIntentions enumerateObjectsUsingBlock:^(TextfieldDelegateIntention *intention, NSUInteger idx, BOOL *stop) {
BOOL isValid = [intention validate];
if (!isValid) {
intention.textField.backgroundColor = [UIColor redColor];
formIsValid = NO;
} else {
intention.textField.backgroundColor = [UIColor greenColor];
}
}];
if (formIsValid) {
if (self.printerPreferecesEntered) {
self.printerPreferecesEntered(#{
#"name": strongSelf.nameTextField.text,
#"ipAddress": strongSelf.ipTextField.text,
#"port": #([strongSelf.portTextField.text integerValue])
});
}
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[strongSelf dismissViewControllerAnimated:YES completion:NULL];
});
}
}
}];
self.okIntention = okIntention;
}
#end
As you see I can use simple blocks to add different behavior to the three textfields and only one method is overwritten — no other added.
Another example with email validation from my blog: Lighter ViewControllers with Block-based Intentions
A tableview's datasource is also very easy implemented as Intention.
#import <UIKit/UIKit.h>
#class PrinterProvider;
#interface PrinterDataSource : NSObject <UITableViewDataSource>
#property (nonatomic, strong) PrinterProvider *printerProvider;
#end
#import "PrinterDataSource.h"
#import "VSPOSNetworkPrinter.h"
#import "PrinterProvider.h"
#interface PrinterDataSource ()
#end
#implementation PrinterDataSource
-(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [[self.printerProvider allPrinters] count];
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"PrinterCell" forIndexPath:indexPath];
cell.textLabel.text = [[self.printerProvider allPrinters][indexPath.row] ipAddress];
cell.detailTextLabel.text = [[self.printerProvider allPrinters][indexPath.row] name];
return cell;
}
#end
Use it as
#import "PrinterViewController.h"
#import "AddPrinterViewController.h"
#import "ButtonIntention.h"
#import "BarButtomItemIntention.h"
#import "NamendPOSNetworkPrinter.h"
#import "PrinterProvider.h"
#import "PrinterDataSource.h"
#interface PrinterViewController ()
#property (weak, nonatomic) IBOutlet UITableView *tableView;
#property (weak, nonatomic) IBOutlet UIBarButtonItem *addButton;
#property (nonatomic, strong) BarButtomItemIntention *addIntention;
#property (nonatomic, strong) AddPrinterViewController *addPrinterViewController;
#property (strong, nonatomic) IBOutlet PrinterDataSource *printerDataSource;
#property (nonatomic, strong) PrinterProvider *printerProvider;
#end
#implementation PrinterViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.printerDataSource.printerProvider = self.printerProvider;
self.addPrinterViewController = [self.storyboard instantiateViewControllerWithIdentifier:#"AddPrinterViewController"];
typeof(self) weakSelf = self;
[self.addPrinterViewController setPrinterPreferecesEntered:^(NSDictionary *printerDict) {
NamendPOSNetworkPrinter *printer = [[NamendPOSNetworkPrinter alloc] initWithName:printerDict[#"name"]
ipAddress:printerDict[#"ipAddress"]
port:printerDict[#"port"]];
typeof(self) strongSelf = weakSelf;
if (strongSelf) {
[strongSelf.printerProvider addPrinter:printer];
[strongSelf.tableView reloadData];
}
}];
self.addPrinterViewController.printerProvider = self.printerProvider;
self.addIntention = [[BarButtomItemIntention alloc] initWithButtonItem:self.addButton
actionBlock:^(UIBarButtonItem *buttonItem)
{
typeof(weakSelf) strongSelf = weakSelf;
if(strongSelf){
[strongSelf presentViewController:strongSelf.addPrinterViewController
animated:YES completion:^{
}];
}
}];
}
#end
The charm about this approach is that you can independently create and subclass view controller and intentions, and that I can rearrange them as needed easily. Actually apple started to advertise a similar approach in the recent wwdc video «Advanced User Interfaces with Collection Views»

Answer 3

I would suggest using #pragma mark [divider name] to split up your class into sections so you can easily group methods. Otherwise creating subclasses where it makes sense to handle contained functionality is you're only option. I've seen 8,000+ line view controller classes, so sometimes it's unavoidable if you're too deep to break it all apart.

Answer 4

This is more like a programming philosophy.
Objective-C has lengthy methods (name and declaration), so the best way to ease the code is to delegate any repetitive pattern to an external class.
For example, I create a class reserved solely of returning numerical operations, such as arithmetic operations on NSNumbers, strings, etc. Another one that just returns booleans on an input.
For example, if you verify the validity of a number and increment it, or set it to 1, in even just two places in your code, rather than having somethings like this:
if (variableName != nil && variableName.intValue > 0)
{
variableName2 = [NSNumber numberWithInt:(variableName.intValue + 1)];
}
else
{
variableName2 = [NSNumber numberWithInt:1];
}
It would be easier to have this function outside (in an "Arithmetics" class for example), and call it like follow:
variableName2 = [Arithmetics incrementNumber:variableName];
If you replace all your code like this, by having well named classes and easy to understand methods (names), your code will be more logically readable and easy to follow, which is the philosophy of Objective-C (you get also the bonus of being able to reuse these methods in all your code, keeping the same logic everywhere).