Foundation框架常用數據類型和NSAutoreleasePool自動釋放池解析

第一、NSAutoreleasePool自動釋放池解析


1、自動釋放池的物理實現


自動釋放池用棧來實現，當你創建一個新的自動釋放池是，會壓棧到棧頂，接受autorelease消息的對象也會被壓入到棧頂
NSAutoreleasePool實現延時釋放，內部包含一個數組（NSMutableArray），用來保存聲名爲autorelease的所有對象。如果一個對象聲明爲autorelease，系統所做的工作就是把這個對象加入到這個數組中去。NSAutoreleasePool自身在銷燬的時候，會遍歷一遍這個數 組，release數組中的每個成員，如果release之後，retain count大於0，此對象依然沒有被銷燬，內存泄露。
2、當我們使用copy、alloc、retain得到一個對象時，必須調用release或者是autorelease進行釋放，其他方法獲得對象將由自動釋放池釋放


3、release和drain的區別


當我們向自動調用【pool release 】時，池內元素都會調用release方法，並且池釋放掉，但是當我們調用drain方法時，只會執行前者


4、自動釋放池的銷燬時間


當我們使用appkit創建工程時，程序會自動創建或排空自動釋放池的對象，通常實在一個時間循環中創建，在結束時排空


5、自動釋放池的作用域與嵌套
AutoreleasePool是可以嵌套使用的，池是被嵌套的，嵌套的結果是個棧，同一線程只有當前棧頂pool實例是可用的：
 當短生命週期內，比如一個循環中，會產生大量的臨時內存，可以創建一個臨時的autorelease pool，這樣可以達到快速回收內存的目的；
 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、自動釋放池帶來的問題
Cocoa應用程序中的每個線程都會維護一個自己的NSAutoreleasePool對象的堆棧。當一個線程終止時，它會自動地釋放所有與自身相關的自動釋放池。在基於Application Kit的應用程序中，自動釋放池會在程序的主線程中被自動創建和銷燬。
● 如果你正在編寫一個不是基於Application Kit的程序，比如命令行工具，則沒有對自動釋放池的內置支持；你必須自己創建它們。
● 如果你生成了一個從屬線程，則一旦該線程開始執行，你必須立即創建你自己的自動釋放池；否則，你將會泄漏對象。
● 如果你編寫了一個循環，其中創建了許多臨時對象，你可以在循環內部創建一個自動釋放池，以便在下次迭代之前銷燬這些對象。這可以幫助減少應用程序的最大內存佔用量
 第四、IOS內存管理的三句話
誰創建，誰釋放：
解釋：通過alloc、new、copy創建的對象，必須調用release、autorelease釋放
誰retain，誰釋放
retain的次數和release、autorelease次數相同
沒創建且沒有retain，別釋放


第二、Foundation FrameWork


定義了多種與基本數據類型類型對應的類，如NSNumber，NSInteger,NSString等，所有從NSSobject繼承創建都是對象


NSArray/NSMutalbeArray, NSDictionary/NSDictionary 包含的對象只能是對象，不能使基本數據類型，應採用NSNumber


mutable表示內容可變，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;
}


關於上述代碼的幾點說明：
1.用類方法創建的對象，不需要release，會自動釋放，用實例方法創建的對象需要release


2.NSArray和NSDictionary可以放各種類型的對象，但不能放基本類型


3.調用函數返回值是對象類型，不需要考慮內存釋放的問題，一般情況下這種返回值會autorelease，遵循誰創建誰釋放的原則


第三、NSDictionary 和 NSMutableDictionary 常用方法詳解
dictionaryWithObjectsAndKeys 用來初始化
objectForKey 用來取值
sample：
NSDictionary *testDic=[NSDictionary dictionaryWithObjectsAndKeys:@"1",@"hello",@"2",@"what", nil];
    NSLog(@"val is %@",[testDic objectForKey:@"hello"]);
NSMutableDictionary可變字典NSMutableDictionary繼承自NSDictionary


常用api：
dictionaryWithCapacity： 用來初始化
setObject: 設置
removeObjectForKey 刪除
[count] 返回字典的數量
[allKeys]獲取所有鍵的集合
[allValues】獲取所有值得集合
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>


返回結果是：
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
)
不經常用的方法爲
- (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如下：
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);




結果：
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 {
}


遍歷字典的方法：
for（id key in dic）
{
 id obj=[dic objectForKey:key];
NSLog(@"%@",obj);
}
一般的枚舉
        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、字符串的創建
創建簡單字符串
NSString *string=@"hello";
創建空字符串
NSString *str2=[[NSStringalloc] init];
NSString *str3=[NSString string];
創建格式化字符串 
NSString *str5=[NSString stringWithFormat:@"hello %d",34]; //是在堆創建的
當用“==”來判斷兩個字符串時，實際上是判斷地址是否相同
下面三個初始化語句的都是在常量區創建的
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);
/*
*定義個string對象，最好初始化，
*/
NSString *str2=@"我7";


stringwithcapacity 用來初始化NSMutableString


2、字符串的比較
compare、isEqualToString ：用來做比較
if([str isEqualToString:str2])
{
NSLog(@"They are the same");
}
/*
* 不區分大小寫 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型的轉換
[str floatValue] 轉換爲float型，[str invValue] 轉換爲整型 
componentsSeparatedByString實現將字符串分割爲數組
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、判斷是否有前綴
hasprefix. hasSuffix: 用來判斷是否有前後綴
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 用來實現追加
*appendString 和 appendFormat實現追加
*/
[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 實現刪除
/*
* deleteCharactersInRange 執行刪除操作
*/
NSRange jackRange;
jackRange=[mulstr rangeOfString:@"ello"];
//jackRange.length++;
[mulstr deleteCharactersInRange:jackRange];
NSLog(@"mulstr:%@",mulstr);


- (void)deleteCharactersInRange:(NSRange)range; 刪除字符串
        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、字符串的查詢
rangeOfString 用來做查詢
typedef struct _NSRange {
     NSUInteger location;  //開始位置
    NSUInteger length;  //長度
} NSRange;
NSRange的定義：
        NSRange range2;
        range2.location = 17;
        range2.length = 4;
        NSLog(@"%lu and  %lu",range2.location,range2.length);
        //用NSMakeRange來初始化
        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 實現字符串的插入
- (void)insertString:(NSString *)aString atIndex:(NSUInteger)loc;
- (void)deleteCharactersInRange:(NSRange)range;


10、改變大小寫


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的詳解
NSArray有兩個限制，首先，只能存儲objective c的對象，不能存儲c語言的基本語言類型，第二，不能包含nil對象
NSArray的用法：
1、初始化
NSArray *firstArray=[[NSArray alloc] initWithObjects:@"one",@"two",@"three", nil];
        NSArray *secondArray=[NSArray arrayWithArray:firstArray];


2、獲取元素個數和訪問
        NSLog(@"the number is %ld",[secondArray count]);
        NSLog(@"the value is %@",[secondArray objectAtIndex:2]);


3、追加數據元素
        NSArray *thirdArray=[firstArray arrayByAddingObjectsFromArray:secondArray];


4、數組轉化爲字符串
        NSString *str=[firstArray componentsJoinedByString:@".."];
        NSLog(@"the number is %@",str);


5、判斷是否包含字符串
        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 的用法-
NSMutableArray是可變的，NSArray是不可變的


6、基本的增刪改
     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、替換操作
        [mutableArr replaceObjectAtIndex:0 withObject:@"kaixin"];


8、遍歷
        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
基本數據類型無法用於字典、集合和數組，爲此，我們需要將基本數據類型封裝成數字對象，在OC中提供了NSNumber解決此問題
1、NSNumber封裝的代碼：
        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!");


結果爲：
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解析的代碼：
        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]);
    }


 創建和初始化類的方法  初始化實例方法     檢索實例方法
 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