在iPhone应用程序中保留全局变量的最佳方法 [英] The best way to keep global variables in iPhone app
问题描述
我是iPhone的新手，所以想问一下，保持全局变量和常量可以被许多类访问的最好方法是什么？
我应该让他们保留在应用程序委托中还是有一种更好的方式，我不知道？
谢谢
将它们保留在应用程序委托中是一种解决方案，但将所有内容都推送到目标类对于常量，您可以简单地创建头文件并使用 #define 或 const ，然后将头文件包含在需要常量的地方。
对于全局变量，您可以创建单身人士课程与 static 变量。有很多宏可以合成类的单例。以下是Google Toolbox for Mac的一个例子：
//
// GTMObjectSingleton.h
/ /宏来实现单身
//
的方法//版权所有2005-2008 Google Inc.
//
//根据Apache许可证版本2.0（执照）;您可能不会
//使用此文件，除非符合许可证。您可以在
//
处获得许可证的复制
// // http://www.apache.org/licenses/LICENSE-2.0
//
//除非适用法律要求或书面同意，否则根据许可证分发的软件
以原样为基础发布，不含
//任何类型的保证或条件，无论是明示还是暗示。请参阅
//许可证，以获取在
//许可证下管理权限和限制的特定语言的许可证。
//
#define _GTMDevAssert（condition，...）\
do {\
if（！（condition））{\
[[NSAssertionHandler currentHandler] \
handleFailureInFunction：[NSString stringWithUTF8String：__ PRETTY_FUNCTION__] \
file：[NSString stringWithUTF8String：__ FILE__] \
lineNumber：__ LINE__ \
描述：__ VA_ARGS__]; \
} \
} while（0）
///这个宏实现了构建安全单例所需的各种方法。
//
///这个单例模式取自：
/// http://developer.apple.com/documentation/Cocoa/Conceptual/CocoaFundamentals/CocoaObjects/chapter_3_section_10.html
///
///示例用法：
///
/// GTMOBJECT_SINGLETON_BOILERPLATE（SomeUsefulManager，sharedSomeUsefulManager）
///（不带尾随分号）
///
#define GTMOBJECT_SINGLETON_BOILERPLATE（_object_name_，_shared_obj_name_）\
static _object_name_ * z ## _ shared_obj_name_ = nil; \
+（_object_name_ *）_ shared_obj_name_ {\
@synchronized（self）{\
if（z ## _ shared_obj_name_ == nil）{\
/ *请注意，'self'可能与_object_name_ * / \
/ *在allocWithZone中完成的第一次分配不同，但如果init失败，我们必须重新分配* / \
z ## _ shared_obj_name_ = [[self alloc] init]; \
_GTMDevAssert（（z ## _ shared_obj_name_！= nil），@没有捕获单例分配）; \
} \
} \
return z ## _ shared_obj_name_; \
} \
+（id）allocWithZone：（NSZone *）zone {\
@synchronized（self）{\
if（z ## _ shared_obj_name_ = =无）{\
z ## _ shared_obj_name_ = [super allocWithZone：zone]; \
return z ## _ shared_obj_name_; \
} \
} \
\
/ *我们无法返回共享实例，因为它已被初始化* / \
_GTMDevAssert（NO，@使用单例API，而不是alloc + init）; \
返回零; \
} \
- （id）retain {\
return self; \
} \
- （NSUInteger）retainCount {\
return NSUIntegerMax; \
} \
- （void）release {\
} \
- （id）autorelease {\
return self; \
} \
- （id）copyWithZone：（NSZone *）zone {\
return self; \
}
I'm new to iPhone development so want to ask, what is the best way to keep global variables and constants which can be accessed by many classes?
Shall I keep them in app delegate or there is a better way which I don't know?
Thanks
Keeping them in the app delegate is one solution, though it's not particularly elegant to shove everything into a class whose purpose is really to respond to events related to the application.
For constants, you can simply create header files and use #define or const, then include the header files wherever you need the constants.
For global variables, you can create a singleton class with static variables. There are a lot of macros out there that can synthesize singletons for classes. Here's an example from the Google Toolbox for Mac:
//
// GTMObjectSingleton.h
// Macro to implement methods for a singleton
//
// Copyright 2005-2008 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy
// of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
//
#define _GTMDevAssert(condition, ...) \
do { \
if (!(condition)) { \
[[NSAssertionHandler currentHandler] \
handleFailureInFunction:[NSString stringWithUTF8String:__PRETTY_FUNCTION__] \
file:[NSString stringWithUTF8String:__FILE__] \
lineNumber:__LINE__ \
description:__VA_ARGS__]; \
} \
} while(0)
/// This macro implements the various methods needed to make a safe singleton.
//
/// This Singleton pattern was taken from:
/// http://developer.apple.com/documentation/Cocoa/Conceptual/CocoaFundamentals/CocoaObjects/chapter_3_section_10.html
///
/// Sample usage:
///
/// GTMOBJECT_SINGLETON_BOILERPLATE(SomeUsefulManager, sharedSomeUsefulManager)
/// (with no trailing semicolon)
///
#define GTMOBJECT_SINGLETON_BOILERPLATE(_object_name_, _shared_obj_name_) \
static _object_name_ *z##_shared_obj_name_ = nil; \
+ (_object_name_ *)_shared_obj_name_ { \
@synchronized(self) { \
if (z##_shared_obj_name_ == nil) { \
/* Note that 'self' may not be the same as _object_name_ */ \
/* first assignment done in allocWithZone but we must reassign in case init fails */ \
z##_shared_obj_name_ = [[self alloc] init]; \
_GTMDevAssert((z##_shared_obj_name_ != nil), @"didn't catch singleton allocation"); \
} \
} \
return z##_shared_obj_name_; \
} \
+ (id)allocWithZone:(NSZone *)zone { \
@synchronized(self) { \
if (z##_shared_obj_name_ == nil) { \
z##_shared_obj_name_ = [super allocWithZone:zone]; \
return z##_shared_obj_name_; \
} \
} \
\
/* We can't return the shared instance, because it's been init'd */ \
_GTMDevAssert(NO, @"use the singleton API, not alloc+init"); \
return nil; \
} \
- (id)retain { \
return self; \
} \
- (NSUInteger)retainCount { \
return NSUIntegerMax; \
} \
- (void)release { \
} \
- (id)autorelease { \
return self; \
} \
- (id)copyWithZone:(NSZone *)zone { \
return self; \
}
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