我在哪里为iOS应用程序创建全局变量？ [英] Where do I create global variables for an iOS app?

问题描述

以下是我的代码：

我希望能够创建一个全局NSMutableArray，它可以存储可以写入.pList文件的Budget *对象。 ..我只知道pLists是什么，我对如何实现它们有点朦胧......

我在哪里错了？

   - （IBAction）btnCreateBudget：（id）sender 
 {
 Budget * [= [[Budget alloc] init ]。 
 
 budget.name = self.txtFldBudgetName.text; 
 budget.amount = [self.txtFldBudgetAmount.text intValue]; 
 
 //将数据写入pList 
 NSMutableArray * anArray = [[NSMutableArray alloc] init]; //我希望这是整个应用程序的全局变量。我在哪里放这个？ 
 
 [anArray addObject：budget]; 
 
 [anArray writeToFile：[self dataFilePath] atomically：YES]; 
 
 / *如您所见，以下是测试代码的地方。不幸的是，每次运行这个命令时，
都只有1个元素。我假设
，这是因为每次按下按钮时，我都会创建一个全新的
 NSMutableArray * anArray。我希望这是整个应用程序的全球性。 * / 
 
 int i = 0; 
（aArray中的Budget * b）
 {
 i ++; 
} 
 NSLog（@anArray中有％d个项目，i）; （NSDocumentDirectory，NSUserDomainMask，YES）; 
 
 
 $ b  - 
 NSString * documentDirectory = [path objectAtIndex：0]; 
 return [documentDirectory stringByAppendingPathComponent：@BudgetData.plist]; 
 
 
 
 
 
 $编辑：我想补充说我创建了anArray数组它可以被其他视图访问。我知道这可以通过NSNotification完成？或者我应该这样做的AppDelegate类？最终目标是让anArray对象填充位于单独视图中的UITableView。
解决方案
只需将声明放在方法而不是内部。
  NSMutableArray * anArray = nil; 
 
  - （IBAction）btnCreateBudget：（id）sender 
 {
 ... 
 if（anArray == nil）
 anArray = [[NSMutableArray alloc] init]; 
 ... 
} 
  
如果仅在一个文件中使用它，使其成为静态来防止与其他文件的名称冲突： 
 
 
  static NSMutableArray * anArray = nil; 
  
如果仅在一个方法中使用它，请将其设置为static并将其放入该方法中：  
 
 
   - （IBAction）btnCreateBudget：（id）sender 
 {
 static NSMutableArray * anArray = nil; 
 ... 
 if（anArray == nil）
 anArray = [[NSMutableArray alloc] init]; 
 ... 
} 
  
请注意，人们通常会使用某种命名全局变量的约定，比如gArray，可以很容易地将它们与局部变量，实例变量或方法参数区分开来。  
Here is my code:


I want to be able to create a global NSMutableArray that can store Budget* objects that can then be written to a .pList file... I'm only learning what pLists are, and I am a bit hazy about how to implement them...

Where am I going wrong here?
- (IBAction)btnCreateBudget:(id)sender 
{
    Budget *budget = [[Budget alloc] init];

    budget.name = self.txtFldBudgetName.text;
    budget.amount = [self.txtFldBudgetAmount.text intValue];    

    // Write the data to the pList
    NSMutableArray *anArray = [[NSMutableArray alloc] init]; // I want this to be a global variable for the entire app. Where do I put this?

    [anArray addObject:budget];

    [anArray writeToFile:[self dataFilePath] atomically:YES];

    /* As you can see, below is where I test the code. Unfortunately, 
    every time I run this, I get only 1 element in the array. I'm assuming 
    that this is because everytime the button is pressed, I create a brand new 
    NSMutableArray *anArray. I want that to be global for the entire app. */

    int i = 0;
    for (Budget * b in anArray)
    {
        i++;
    }
    NSLog(@"There are %d items in anArray",i);

}

-(NSString *) dataFilePath
{ 
    NSArray *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
    NSString *documentDirectory = [path objectAtIndex:0]; 
    return [documentDirectory stringByAppendingPathComponent:@"BudgetData.plist"];
}
edit: I'd like to add that I am creating the anArray array so that it can be accessible by other views. I understand that this can be done with NSNotification? or Should I do this the appDelegate classes? The end goal is to have the anArray object populate a UITableView that is in a separate View.
解决方案
Just put the declaration outside the method instead of inside it.
NSMutableArray *anArray = nil;

- (IBAction)btnCreateBudget:(id)sender 
{
    ...
    if ( anArray == nil )
      anArray = [[NSMutableArray alloc] init]; 
    ...
}
If it's only used inside the one file, make it "static" instead to prevent name collisions with other files: 
    static NSMutableArray *anArray = nil;
If it's only used inside the one method, make it "static" and put it inside that method:
- (IBAction)btnCreateBudget:(id)sender 
{
    static NSMutableArray *anArray = nil;
    ...
    if ( anArray == nil )
      anArray = [[NSMutableArray alloc] init]; 
    ...
}
Note that people usually use some kind of naming convention for global variables, like "gArray", to easily differentiate them from local variables, instance variables, or method parameters. 

                        
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