Foundation框架经常使用数据类型和NSAutoreleasePool自己主动释放池解析

第一、NSAutoreleasePool自己主动释放池解析





1、自己主动释放池的物理实现





自己主动释放池用栈来实现。当你创建一个新的自己主动释放池是，会压栈到栈顶。接受autorelease消息的对象也会被压入到栈顶

NSAutoreleasePool实现延时释放，内部包括一个数组（NSMutableArray）。用来保存声名为autorelease的全部对象。假设一个对象声明为autorelease，系统所做的工作就是把这个对象增加到这个数组中去。

NSAutoreleasePool自身在销毁的时候，会遍历一遍这个数 组，release数组中的每一个成员，假设release之后，retain count大于0。此对象依旧没有被销毁，内存泄露。

2、当我们使用copy、alloc、retain得到一个对象时。必须调用release或者是autorelease进行释放。其它方法获得对象将由自己主动释放池释放





3、release和drain的差别





当我们向自己主动调用【pool release 】时，池内元素都会调用release方法，而且池释放掉。可是当我们调用drain方法时，仅仅会运行前者





4、自己主动释放池的销毁时间





当我们使用appkit创建project时，程序会自己主动创建或排空自己主动释放池的对象，通常实在一个时间循环中创建，在结束时排空





5、自己主动释放池的作用域与嵌套

AutoreleasePool是能够嵌套使用的，池是被嵌套的。嵌套的结果是个栈，同一线程仅仅有当前栈顶pool实例是可用的：

 当短生命周期内，比方一个循环中。会产生大量的暂时内存，能够创建一个暂时的autorelease pool。这样能够达到高速回收内存的目的。

 NSAutoreleasePool *pool;

    pool=[[NSAutoreleasePool alloc] init];

    {

        for (int i=0; i<100000; i++)

        {

            NSObject *obj=[[[NSObject alloc] init] autorelease];

            NSLog(@"the obj is%@",obj);





            if(i%10000==0)

            {

                [pool drain];

                pool=[[NSAutoreleasePool alloc] init];





            }

        }

    }

    [pool drain];





6、自己主动释放池带来的问题

Cocoa应用程序中的每一个线程都会维护一个自己的NSAutoreleasePool对象的堆栈。当一个线程终止时。它会自己主动地释放全部与自身相关的自己主动释放池。在基于Application Kit的应用程序中。自己主动释放池会在程序的主线程中被自己主动创建和销毁。

● 假设你正在编写一个不是基于Application Kit的程序，比方命令行工具，则没有对自己主动释放池的内置支持。你必须自己创建它们。

● 假设你生成了一个从属线程，则一旦该线程開始运行，你必须马上创建你自己的自己主动释放池。否则，你将会泄漏对象。

● 假设你编写了一个循环，当中创建了很多暂时对象。你能够在循环内部创建一个自己主动释放池，以便在下次迭代之前销毁这些对象。

这能够帮助降低应用程序的最大内存占用量

 第四、IOS内存管理的三句话

谁创建，谁释放：

解释：通过alloc、new、copy创建的对象，必须调用release、autorelease释放

谁retain，谁释放

retain的次数和release、autorelease次数同样

没创建且没有retain，别释放





第二、Foundation FrameWork





定义了多种与基本数据类型类型相应的类，如NSNumber，NSInteger,NSString等，全部从NSSobject继承创建都是对象





NSArray/NSMutalbeArray, NSDictionary/NSDictionary 包括的对象仅仅能是对象。不能使基本数据类型，应採用NSNumber





mutable表示内容可变，非mubable

NSString和NSMutableString





int main(int argc, const char * argv[])

{

    //NSArray *colors=[NSArray arrayWithObjects:@"hello",@"richard",@"yang", nil];

    NSString *str=[NSString stringWithFormat:@"hello,richard,yang"];

    NSArray *arr=[str componentsSeparatedByString:@","];

    NSLog(@"retaincount is% ld",[str retainCount]);

    for(int i=0;i<arr.count;i++)

    {

        NSLog(@"The element is %s",[[arr objectAtIndex:i] UTF8String]);

    }

    NSNumber *myNum=[NSNumber numberWithInt:3];

    NSLog(@"the val is %@",myNum);

    

    NSMutableArray *array=[[NSMutableArray alloc] initWithCapacity:4];

    [array addObject:@"hello"];

    [array insertObject:@"what " atIndex:1];

    NSLog(@"THE LAST IS %@",[array lastObject]);

    return 0;

}





关于上述代码的几点说明：

1.用类方法创建的对象。不须要release，会自己主动释放。用实例方法创建的对象须要release





2.NSArray和NSDictionary能够放各种类型的对象。但不能放基本类型





3.调用函数返回值是对象类型，不须要考虑内存释放的问题，普通情况下这样的返回值会autorelease。遵循谁创建谁释放的原则





第三、NSDictionary 和 NSMutableDictionary 经常用法具体解释

dictionaryWithObjectsAndKeys 用来初始化

objectForKey 用来取值

sample：

NSDictionary *testDic=[NSDictionary dictionaryWithObjectsAndKeys:@"1",@"hello",@"2",@"what", nil];

    NSLog(@"val is %@",[testDic objectForKey:@"hello"]);

NSMutableDictionary可变字典NSMutableDictionary继承自NSDictionary





经常使用api：

dictionaryWithCapacity： 用来初始化

setObject: 设置

removeObjectForKey 删除

[count] 返回字典的数量

[allKeys]获取全部键的集合

[allValues】获取全部值得集合

sample:

NSMutableDictionary *testDic=[NSMutableDictionary dictionaryWithCapacity:12];

        [testDic setObject:@"1" forKey:@"hel"];

        [testDic setObject:@"2da" forKey:@"what"];

        [testDic setObject:@"hello" forKey:@"hello"];

        NSLog(@"the val is %@",[testDic objectForKey:@"what"]);

        NSLog(@"the length is %ld",[testDic count]);

        [testDic removeObjectForKey:@"hello"];

        NSLog(@"the length is %lu",testDic.count);

        

        NSArray *keyArray=[testDic allKeys];

        NSArray *valArray=[testDic allValues];

        NSLog(@"the all keys are %@",keyArray);

        NSLog(@"the all values are %@",valArray);

    }





</span>





返回结果是：

2013-10-09 17:20:19.533 element[401:303] the val is 2da

2013-10-09 17:20:19.535 element[401:303] the length is 3

2013-10-09 17:20:19.536 element[401:303] the length is 2

2013-10-09 17:20:19.537 element[401:303] the all keys are (

    what,

    hel

)

2013-10-09 17:20:19.537 element[401:303] the all values are (

    2da,

    1

)

不经经常使用的方法为

- (void)addEntriesFromDictionary:(NSDictionary *)otherDictionary;

- (void)removeAllObjects;

- (void)removeObjectsForKeys:(NSArray *)keyArray;

- (void)setDictionary:(NSDictionary *)otherDictionary;

- (void)setObject:(id)obj forKeyedSubscript:(id <NSCopying>)keyNS_AVAILABLE(10_8,6_0);

sample例如以下：

NSMutableDictionary *emptyDic=[NSMutableDictionary dictionary];

        [emptyDic setValue:@"2" forKey:@"2"];

        NSLog(@"empty DIC is %@",emptyDic);

        NSMutableDictionary *testDic=[NSMutableDictionary dictionaryWithObjectsAndKeys:@"hello",@"1",@"andy",@"2",@"yang",@"3",nil];

        

        NSDictionary *dic4=[NSDictionary dictionaryWithObject:@"yang" forKey:@"4"];

        [testDic addEntriesFromDictionary:dic4];

        NSLog(@"the mutalble dictionary is %@",testDic);

        [emptyDic setDictionary:testDic];

        NSLog(@"empty DIC is %@",emptyDic);

        

        NSArray *deleteArr=[NSArray arrayWithObjects:@"1",@"2",@"yang",nil];

        [testDic removeObjectsForKeys:deleteArr];

        NSLog(@"the mutalble dictionary is %@",testDic);

        

        [testDic removeAllObjects];

        NSLog(@"the mutalble dictionary is %@",testDic);









结果：

2013-10-09 17:39:37.832 element[463:303] empty DIC is {

    2 = 2;

}

2013-10-09 17:39:37.834 element[463:303] the mutalble dictionary is {

    1 = hello;

    2 = andy;

    3 = yang;

    4 = yang;

}

2013-10-09 17:39:37.834 element[463:303] empty DIC is {

    1 = hello;

    2 = andy;

    3 = yang;

    4 = yang;

}

2013-10-09 17:39:37.835 element[463:303] the mutalble dictionary is {

    3 = yang;

    4 = yang;

}

2013-10-09 17:39:37.835 element[463:303] the mutalble dictionary is {

}





遍历字典的方法：

for（id key in dic）

{

 id obj=[dic objectForKey:key];

NSLog(@"%@",obj);

}

一般的枚举

        NSMutableDictionary *testDic=[NSMutableDictionarydictionaryWithObjectsAndKeys:@"hello",@"1",@"andy",@"2",@"yang",@"3",nil];

        for(int index=0;index<[testDiccount];index++)

        {

            NSString *obj=[testDic objectForKey:[[testDic allKeys] objectAtIndex:index]];

            NSLog(@"the val is %@",obj);

        }

        

        for(id key in testDic)

        {

            NSString *obj2=[testDic objectForKey:key];

            NSLog(@"the val is %@",obj2);

        }

第四、NSString 和NSMutableString 使用技巧

1、字符串的创建

创建简单字符串

NSString *string=@"hello";

创建空字符串

NSString *str2=[[NSStringalloc] init];

NSString *str3=[NSString string];

创建格式化字符串 

NSString *str5=[NSString stringWithFormat:@"hello %d",34]; //是在堆创建的

当用“==”来推断两个字符串时，实际上是推断地址是否同样

以下三个初始化语句的都是在常量区创建的

NSString *string1=@"hello";

NSString *string2=[NSString stringWithString:@"hello"];

NSString *string1=[[NSString alloc] initWithString:@"hello"];

if (string1==string2) {

NSLog(@"they are same");

}

/**

* 字符串的格式化stringWithFormat 

*/

NSString *str=[NSString stringWithFormat:@"我%d",7];

NSLog(@"str:%@",str);

/*

*length supoort chinese

*/

unsigned int lengh=(unsigned int)[str length];

NSLog(@"length:%d",lengh);

/*

*定义个string对象，最好初始化，

*/

NSString *str2=@"我7";





stringwithcapacity 用来初始化NSMutableString





2、字符串的比較

compare、isEqualToString ：用来做比較

if([str isEqualToString:str2])

{

NSLog(@"They are the same");

}

/*

* 不区分大写和小写 compare options

*/

NSString *str3=@"Block";

NSString *str4=@"block";

if([str3 compare:str4 options:NSCaseInsensitiveSearch]==0)

{

NSLog(@"insensitive same");

}









3、字符串和float、int型的转换

[str floatValue] 转换为float型，[str invValue] 转换为整型 

componentsSeparatedByString实现将字符串切割为数组

NSString *test=[NSString stringWithFormat:@"3.14"];

float f=[test floatValue];

NSLog(@"float val is %.2f",f);





int i=[test intValue];

NSLog(@"the int val is %i",i);





NSString *str=[NSString stringWithFormat:@"one two three"];

NSArray *arr=[str componentsSeparatedByString:@" "];

NSLog(@"the arr is %@",arr);









4、截取字符串





substringFromIndex、

substringToIndex、

substringWithRange

NSString *str=[NSString stringWithFormat:@"onetwothree"];

NSString *substr=[str substringFromIndex:2];

NSString *substr2=[str substringToIndex:3];

NSLog(@"the arr is %@",substr);

NSLog(@"the arr is %@",substr2);

NSRange range;

range.length=4;

range.location=2;

NSString *substr3=[str substringWithRange:range];

NSLog(@"the arr is %@",substr3);





5、推断是否有前缀

hasprefix. hasSuffix: 用来推断是否有前后缀

NSString *str5=@"draft-hello.mov";

NSString *str6=@"draft";

NSString *str7=@"mov";

if([str5 hasPrefix:str6])

{

NSLog(@"str5 has prefix str6");

}

if([str5 hasSuffix:str7])

{

NSLog(@"str5 has suffix str7");

}





6、字符串的拼接

appendString,appendFormat 用来实现追加

*appendString 和 appendFormat实现追加

*/

[mulstr appendString:@"hello"];

NSLog(@"%@",mulstr);

[mulstr appendFormat:@"hello %d",12];

NSLog(@"%@",mulstr);





NSString *str=[NSString stringWithFormat:@"onetwothree"];

NSString *substr2=[str substringToIndex:3];

NSString *substr3=[substr2 stringByAppendingString:@"hello"];

NSLog(@"the arr is %@",substr3);













7、deleteCharactersInRange 实现删除

/*

* deleteCharactersInRange 运行删除操作

*/

NSRange jackRange;

jackRange=[mulstr rangeOfString:@"ello"];

//jackRange.length++;

[mulstr deleteCharactersInRange:jackRange];

NSLog(@"mulstr:%@",mulstr);





- (void)deleteCharactersInRange:(NSRange)range; 删除字符串

        NSMutableString *str1=[NSMutableString stringWithFormat:

        @"hello what is your name?"];

        NSRange range;

        range=[str1 rangeOfString:@"what"];

        NSLog(@"start is %lu,length is %lu",range.location,range.length);

        [str1 deleteCharactersInRange:range];

        NSLog(@"str is %@",str1);









8、字符串的查询

rangeOfString 用来做查询

typedef struct _NSRange {

     NSUInteger location;  //開始位置

    NSUInteger length;  //长度

} NSRange;

NSRange的定义：

        NSRange range2;

        range2.location = 17;

        range2.length = 4;

        NSLog(@"%lu and  %lu",range2.location,range2.length);

        //用NSMakeRange来初始化

        NSRange rang1=NSMakeRange(12, 23);

        NSLog(@" %lu and %lu",rang1.location,rang1.length);





NSString *str=[NSString stringWithFormat:@"onetwothree"];

NSRange range=[str rangeOfString:@"two"];

if(range.location!=NSNotFound)

{

NSLog(@"the arr is %@",str);

}else

{

NSLog(@"hello");

}









9、NSMutableString 实现字符串的插入

- (void)insertString:(NSString *)aString atIndex:(NSUInteger)loc;

- (void)deleteCharactersInRange:(NSRange)range;





10、改变大写和小写





NSString *myString=@"hello WOrld";

NSLog(@"the upper string is %@",[myString uppercaseString]);

NSLog(@"the lower string is %@",[myString lowercaseString]);

NSLog(@"the cap string is %@",[myString capitalizedString]);





第五、NSArray和NSMutableArray的具体解释

NSArray有两个限制。首先，仅仅能存储objective c的对象，不能存储c语言的基本语言类型，第二。不能包括nil对象

NSArray的使用方法：

1、初始化

NSArray *firstArray=[[NSArray alloc] initWithObjects:@"one",@"two",@"three", nil];

        NSArray *secondArray=[NSArray arrayWithArray:firstArray];





2、获取元素个数和訪问

        NSLog(@"the number is %ld",[secondArray count]);

        NSLog(@"the value is %@",[secondArray objectAtIndex:2]);





3、追加数据元素

        NSArray *thirdArray=[firstArray arrayByAddingObjectsFromArray:secondArray];





4、数组转化为字符串

        NSString *str=[firstArray componentsJoinedByString:@".."];

        NSLog(@"the number is %@",str);





5、推断是否包括字符串

        NSArray *firstArray=[[NSArray alloc] initWithObjects:@"one",@"two",@"three", nil];

        NSLog(@"has value %d",[firstArray containsObject:@"two"]);

        NSLog(@"has value %ld",[firstArray indexOfObject:@"two"]);

        NSLog(@"the last object is %@",[firstArray lastObject]);





NSMutalbeArray 的使用方法-

NSMutableArray是可变的，NSArray是不可变的





6、主要的增删改

     NSMutableArray *mutableArr=[NSMutableArray arrayWithCapacity:4];

        [mutableArr addObject:@"hello"];

        [mutableArr addObject:@"hello"];

        [mutableArr addObject:@"hello"];





        [mutableArr addObject:@"richard"];

        [mutableArr insertObject:@"yang" atIndex:1];

        NSLog(@"%@",mutableArr);

        [mutableArr removeObject:@"hello"];

        [mutableArr removeObjectAtIndex:0];

        [mutableArr removeLastObject];

        NSLog(@"%@",mutableArr);





7、替换操作

        [mutableArr replaceObjectAtIndex:0 withObject:@"kaixin"];





8、遍历

        NSMutableArray *mutableArr=[NSMutableArray arrayWithCapacity:4];

        [mutableArr addObject:@"hello"];

        [mutableArr addObject:@"hello"];

        [mutableArr addObject:@"hello"];

        for(int index=0;index<[mutableArr count];index++)

        {

            NSLog(@"the val is %@",[mutableArr objectAtIndex:index]);

        }

        for(NSString *str in mutableArr)

        {

            NSLog(@"%@",str);

        }

        for (id str in mutableArr) {

            NSLog(@"%@",str);

        }

第五、NSNumber的使用

基本数据类型无法用于字典、集合和数组。为此。我们须要将基本数据类型封装成数字对象。在OC中提供了NSNumber解决此问题

1、NSNumber封装的代码：

        int age=12;

        NSNumber *num1=[NSNumber numberWithInt:age];

        NSNumber *num2=[NSNumber numberWithFloat:10.8];

        NSLog(@"the val is %@",num1);

        NSLog(@"the val is %@",num2);

        NSDictionary *dic=[NSDictionary dictionaryWithObjectsAndKeys:num1,@"age",num2,@"info", nil];

        // insert code here...

        NSLog(@"%@",dic);

        NSLog(@"Hello, World!");





结果为：

2013-10-08 17:50:58.777 element[1731:303] the val is 12

2013-10-08 17:50:58.779 element[1731:303] the val is 10.8

2013-10-08 17:50:58.779 element[1731:303] {

    age = 12;

    info = "10.8";

}

2013-10-08 17:50:58.780 element[1731:303] Hello, World!









2、NSNumber解析的代码：

        int age=12;

        NSNumber *num1=[NSNumber numberWithInt:age];

        NSNumber *num2=[NSNumber numberWithFloat:10.8];

        NSLog(@"the num is %d",[num1 intValue]);

        NSLog(@"the num is %d",[num2 intValue]);

    }





 创建和初始化类的方法  初始化实例方法     检索实例方法

 numberWithChar:     initWithChar:   charValue

 numberWithUnsignedChar:     initWithUnsignedChar:   unsignedCharValue

 numberWithShort:    initWithShort:  shortValue

 numberWithUnsignedShort:    initWithUnsignedShort:  unsignedShortValue

 numberWithInteger:  initWithInteger:    integerValue

 numberWithUnsignedInteger:  initWithUnsignedInteger:    unsignedIntegerValue

 numberWithInt:  initWithInt:    intValueunsigned

 numberWithUnsignedInt:  initWithUnsignedInt:    unsignedIntValue

 numberWithLong:     initWithLong:   longValue

 numberWithUnsignedLong:     initWithUnsignedLong:   unsignedLongValue

 numberWithLongLong:     initWithLongLong:   longlongValue

 numberWithUnsignedLongLong:     initWithUnsignedLongLong:   unsignedLongLongValue

 numberWithFloat:    initWithFloat:  floatValue

 numberWithDouble:   initWithDouble:     doubleValue

 numberWithBool:     initWithBool:   boolValue