Question

我正在创建一个简单的小费计算器来学习iOS开发的基础知识，但我无法从一个页面保存值并在另一个页面中重复使用它。

目前，我的根页面（又名TipViewController.m）：

#import "TipViewController.h"
#import "SettingsViewController.h"

@interface TipViewController ()

@property (weak, nonatomic) IBOutlet UITextField *billTextField;
@property (weak, nonatomic) IBOutlet UILabel *tipLabel;
@property (weak, nonatomic) IBOutlet UILabel *totalLabel;
@property (weak, nonatomic) IBOutlet UISegmentedControl *tipControl;

- (IBAction)onTap:(id)sender;
- (void)updateValues;
- (void)onSettingsButton;

@end

@implementation TipViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        self.title = @"Tip Calculator";
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self updateValues];
    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Settings" style:UIBarButtonItemStylePlain target:self action:@selector(onSettingsButton)];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)onTap:(id)sender {
    [self.view endEditing:YES]; //keyboard goes away
    [self updateValues];
}

- (void)updateValues{
    float billAmount = [self.billTextField.text floatValue];

    // array to hold all tip values
    NSArray *tipValues = @[@(0.1), @(0.15), @(0.2)];
    float tipAmount = billAmount*[tipValues[self.tipControl.selectedSegmentIndex] floatValue];
    float totalAmount = tipAmount + billAmount;

    self.tipLabel.text = [NSString stringWithFormat:@"$%0.2f", tipAmount];
    self.totalLabel.text = [NSString stringWithFormat:@"$%0.2f", totalAmount];
}

- (void)onSettingsButton {
    [self.navigationController pushViewController:[[SettingsViewController alloc] init] animated:YES];
}

@end

当我点击右上方的设置按钮时，它会引导我进入我的设置页面：

#import "SettingsViewController.h"

@interface SettingsViewController ()
@property (weak, nonatomic) IBOutlet UITextField *defaultTipPercentage;

- (IBAction)ontap:(id)sender;

@end

@implementation SettingsViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        self.title = @"Settings";
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.

}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}


- (IBAction)ontap:(id)sender {

    [self.view endEditing:YES];
}
@end

现在我希望TextField中的值成为我返回根页面时使用的默认提示百分比。

我想把它放在ontap()下以保存值（SettingsViewController.m）：

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:@"some_string_to_save" forKey:@"some_key_that_you_choose"];
[defaults setInteger:123 forKey:@"another_key_that_you_choose"];
[defaults synchronize];

在我的if statement中的updateValues()内创建TipViewController.m以加载默认值。

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString *stringValue = [defaults objectForKey:@"some_key_that_you_choose"];
int intValue = [defaults integerForKey:@"another_key_that_you_choose"];

- (void)updateValues{
    float billAmount = [self.billTextField.text floatValue];

    if (intValue) {
        float tipAmount = .01 * intValue;
    }else {

    // array to hold all tip values
    NSArray *tipValues = @[@(0.1), @(0.15), @(0.2)];
    float tipAmount = billAmount*[tipValues[self.tipControl.selectedSegmentIndex] floatValue];
    float totalAmount = tipAmount + billAmount;
    }

    self.tipLabel.text = [NSString stringWithFormat:@"$%0.2f", tipAmount];
    self.totalLabel.text = [NSString stringWithFormat:@"$%0.2f", totalAmount];
}

我不确定我是否正确这样做，但这是我到目前为止所尝试过的。

Answer 1

rdelmar评论是正确的，除非您确实希望在应用程序的启动之间保持该值。（在这种情况下，我会这么认为。）移动线

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
int intValue = [defaults integerForKey:@"another_key_that_you_choose"];

在updateValues内，因此每次调用intValue时updateValues的值都是最新的。

保存和使用值提示计算器应用程序

1 个答案: