ios - 如何声明静态变量？
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ios - How to declare static variable?
提问by user2439531
Static Variable declared in C# like this :
在 C# 中声明的静态变量如下：
private const string Host = "http://80dfgf7c22634nbbfb82339d46.cloudapp.net/";
private const string ServiceEndPoint = "DownloadService.svc/";
private const string ServiceBaseUrl = Host + ServiceEndPoint;
public static readonly string RegisteredCourse = ServiceBaseUrl + "RegisteredCourses";
public static readonly string AvailableCourses = ServiceBaseUrl + "Courses";
public static readonly string Register = ServiceBaseUrl + "Register?course={0}";
How to call this static variable in another class ?
如何在另一个类中调用这个静态变量？
回答by Bhavin
Answer :use the statickeyword.
答：使用static关键字。
Syntax :static ClassName *const variableName = nil;( Updated [ Added const]as per the Comment by Abizern)
语法：（根据Abilern的评论static ClassName *const variableName = nil;更新[添加const]）
Reason for update ( As per the comments by "Till " ):
staticwhen being used on a variable within a function/method will preserve its state even when the scope of that variable is left. When being used outside any function/method, it will make that variable invisible to other source files - it will be visible within that implementation file only when being used outside any function/method.
Hence a constwith statichelps the compiler to optimize it accordingly.
更新原因（根据“Till”的评论）：
static当在函数/方法中的变量上使用时，即使该变量的作用域已离开，也将保留其状态。当在任何函数/方法之外使用时，它将使该变量对其他源文件不可见 - 只有在任何函数/方法之外使用时，它才会在该实现文件中可见。因此constwithstatic帮助编译器相应地优化它。
If you need more explanation on use of constwith static, I found one beautiful link here : const static.
如果您需要更多有关constwith 的使用说明static，我在这里找到了一个漂亮的链接：const static。
Use:
用：
You might have seen the use of "static"keyword in your tableview's delegate - cellForRowAtIndexPath:
您可能已经在 tableview 的委托中看到了“static”关键字的使用- cellForRowAtIndexPath:
static NSString *CellIdentifier = @"reuseStaticIdentifier";
static NSString *CellIdentifier = @"reuseStaticIdentifier";
回答by MaxGabriel
static NSString *aString = @""; // Editable from within .m file
NSString * const kAddressKey = @"address"; // Constant, visible within .m file
// in header file
extern NSString * const kAddressKey; // Public constant. Use this for e.g. dictionary keys.
To my knowledge public statics aren't a built-in feature of Objective-C. You can work around this by making a public class method that returns the static variable:
据我所知，公共静态不是 Objective-C 的内置功能。您可以通过创建一个返回静态变量的公共类方法来解决此问题：
//.h
+ (NSString *)stringVariable;
//.m
static NSString * aString;
+ (NSString *)stringVariable
{
return aString;
}
Most static objects can't be initialized at compile time (I think only strings actually). If you need to initialize them, you can do so in the + (void)initializemethod, which lazily gets called whenever that class is first referenced.
大多数静态对象不能在编译时初始化（我认为实际上只有字符串）。如果您需要初始化它们，您可以在+ (void)initialize方法中进行，只要第一次引用该类，就会延迟调用该方法。
static UIFont *globalFont;
+ (void)initialize
{
// Prevent duplicate initialize http://www.mikeash.com/pyblog/friday-qa-2009-05-22-objective-c-class-loading-and-initialization.html
if (self == [ClassName class]) {
globalFont = [UIFont systemFontOfSize:12];
}
}
回答by Amitg2k12
Objective C is super set of C/C++ , so for static it follows C++/C convention, you should be able to use it
Objective C 是 C/C++ 的超集，因此对于静态它遵循 C++/C 约定，您应该可以使用它
static <<datatype>> <<variableName>> = initialization
Hoping you would have tried this way , have you got any error, if yes, please add more clarity in your question
希望您尝试过这种方式，您是否有任何错误，如果是，请在您的问题中更加明确
if thats case with NSStringuse following,
如果NSString使用以下的情况，
static NSString *pString = @"InitialValue";
and if you have to modify NSStringin your code, make sure it must be NSMutableString.
如果您必须修改NSString代码，请确保它必须是NSMutableString.
Hope that's help ...
希望这有帮助...
