不了解全局变量 [英] Don't understand global variables

问题描述

我正在为iPad开发一款应用程序，通常需要共享变量。对我来说，最简单的解决方案似乎是用全局变量创建一个类，而不是关注来回传递 - 因为我也遇到了一些问题。

在Objective-C中为iOS IOS7创建和使用全局变量的最简单方法是使用Xcode 5和故事板？

（我知道有重复但我可以'让它工作）

解决方案

编辑：关注@nhgrif和其他评论， em>

传递变量或使用全局变量的方式实际上取决于您试图做什么。

以下是几种方法：
$ b 将值从一个视图传递到另一个视图可以在添加到堆栈之前完成，如下所示：

/ p>

  ViewController * viewController = [[ViewController alloc] init]; 
 viewController.yourIntegerValue = 42; 
 [self presentViewController：viewController animated：YES completion：nil]; 
  

NSUserDefaults 非常适合您希望通过的通用小数据块围绕或保存供以后使用。请参阅AlwaysWannaLearn的示例，我通常为所有通用值（使用键）构建和存储NSDictionary。
（另请参阅我同意的@nhgrif评论）

AppDelegate 解决方案是另一种方式，因为@Martin Koles建议。也许可以用一套价值，如果仅仅是为了将所有的全局变量放在一个地方，我会避免它。

Singleton 解决方案（原始答案）。
它简单，可扩展，优雅和高效。我通常会将其中一个添加到我创建的任何项目中。

快速操作：

创建一个新文件：MyManager.h

  #import< foundation / Foundation.h> 
 
 @interface MyManager：NSObject {
 NSString * someProperty; 
} 
 
 @property（nonatomic，retain）NSString * someProperty; 
 
 +（id）sharedManager; 
 
 @end 
  

创建一个新文件：MyManager.m

  #importMyManager.h
 
 @implementation MyManager 
 
 @synthesize someProperty ; 
 
 #pragma标记Singleton方法
 $ b $（b）（id）sharedManager {
 static MyManager * sharedMyManager = nil; 
 static dispatch_once_t onceToken; 
 dispatch_once（& onceToken，^ {
 sharedMyManager = [[self alloc] init]; 
}）; 
返回sharedMyManager; 
 
 $ b  - （id）init {
 if（self = [super init]）{
 someProperty = [[NSString alloc] initWithString：@Default Property值]; 
} 
返回自我; 
} 
 
  - （void）dealloc {
 //永远不要被调用，但为了清晰起见，这里真的很简单。 
} 
 
 @end 
  

-
此类将保存您的全局函数和值

要使用这个漂亮的技巧，请将以下行粘贴到项目的其他任何位置 p>

  MyManager * sharedManager = [MyManager sharedManager]; 
 // int getValuefromSingleton = sharedManager.MyFunctionOrValue; 
  

I'm developing an app for iPad that often needs to share variables. Too me it seems like the easiest solution would be to create a class with global variables instead of focusing on passing back and forth - as I've also had some problems with that.

What's the easiest way to create and use global variables in objective-C for iPad IOS7 using Xcode 5 with storyboards?

(I know there are duplicates but I can't make it work)

解决方案

Edit: following @nhgrif and others comments, I am slightly changing my answer

The way to pass variables or use global variables really depends on what you try to do.

Here are few ways:

Passing a value from one view to the other can simply be done before adding it to the stack as so:

ViewController *viewController = [[ViewController alloc] init];
viewController.yourIntegerValue =  42;   
[self presentViewController:viewController animated:YES completion:nil];

NSUserDefaults are great for generic small chunks of data which you like to pass around or save for later use. see example from AlwaysWannaLearn, I usually build and store NSDictionary for all the generic value (with keys). (also see comment from @nhgrif which I agree with)

AppDelegate solution is another way to go as @Martin Koles suggested. Perhaps ok for a single set of value, I would avoid it if just for the sake of having all my globals in one place.

Singleton solution (original answer). it is simple, expandable, elegant and efficient. I usually add one of them to any project I create.

here is how to do it quickly:

create a new file : MyManager.h

#import <foundation/Foundation.h>

@interface MyManager : NSObject {
    NSString *someProperty;
}

@property (nonatomic, retain) NSString *someProperty;

+ (id)sharedManager;

@end

create a new file : MyManager.m

#import "MyManager.h"

@implementation MyManager

@synthesize someProperty;

#pragma mark Singleton Methods

+ (id)sharedManager {
    static MyManager *sharedMyManager = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedMyManager = [[self alloc] init];
    });
    return sharedMyManager;
}

- (id)init {
  if (self = [super init]) {
      someProperty = [[NSString alloc] initWithString:@"Default Property Value"];
  }
  return self;
}

- (void)dealloc {
  // Should never be called, but just here for clarity really.
}

@end

Thats it really - this class will hold your global functions and values

To use this nifty trick , paste the following line anywhere else in your project

MyManager *sharedManager = [MyManager sharedManager];
//int getValuefromSingleton = sharedManager.MyFunctionOrValue;

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