第一、NSAutoreleasePool自动释放池解析
1、自动释放池的物理实现
自动释放池用栈来实现，当你创建一个新的自动释放池是，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，内部包含一个数组（NSMutableArray），用来保存声名为autorelease的所有对象。如果一个对象声明为autorelease，系统所做的工作就是把这个对象加入到这个数组中去。NSAutoreleasePool自身在销毁的时候，会遍历一遍这个数 组，release数组中的每个成员，如果release之后，retain count大于0，此对象依然没有被销毁，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，其他方法获得对象将由自动释放池释放
3、release和drain的区别
当我们向自动调用【pool release 】时，池内元素都会调用release方法，并且池释放掉，但是当我们调用drain方法时，只会执行前者
4、自动释放池的销毁时间
当我们使用appkit创建工程时，程序会自动创建或排空自动释放池的对象，通常实在一个时间循环中创建，在结束时排空
5、自动释放池的作用域与嵌套
AutoreleasePool是可以嵌套使用的，池是被嵌套的，嵌套的结果是个栈，同一线程只有当前栈顶pool实例是可用的：
当短生命周期内，比如一个循环中，会产生大量的临时内存，可以创建一个临时的autorelease pool，这样可以达到快速回收内存的目的；
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、自动释放池带来的问题
Cocoa应用程序中的每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，它会自动地释放所有与自身相关的自动释放池。在基于Application Kit的应用程序中，自动释放池会在程序的主线程中被自动创建和销毁。
● 如果你正在编写一个不是基于Application Kit的程序，比如命令行工具，则没有对自动释放池的内置支持；你必须自己创建它们。
● 如果你生成了一个从属线程，则一旦该线程开始执行，你必须立即创建你自己的自动释放池；否则，你将会泄漏对象。
● 如果你编写了一个循环，其中创建了许多临时对象，你可以在循环内部创建一个自动释放池，以便在下次迭代之前销毁这些对象。这可以帮助减少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次数相同
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对应的类，如NSNumber，NSInteger,NSString等，所有从NSSobject继承创建都是对象
NSArray/NSMutalbeArray, NSDictionary/NSDictionary 包含的对象只能是对象，不能使基本数据类型，应采用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，不需要release，会自动释放，用实例方法创建的对象需要release
2.NSArray和NSDictionary可以放各种类型的对象，但不能放基本类型
3.调用函数返回值是对象类型，不需要考虑内存释放的问题，一般情况下这种返回值会autorelease，遵循谁创建谁释放的原则
第三、NSDictionary 和 NSMutableDictionary 常用方法详解
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
常用api：
dictionaryWithCapacity： 用来初始化
setObject: 设置
removeObjectForKey 删除
[count] 返回字典的数量
[allKeys]获取所有键的集合
[allValues】获取所有值得集合
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
)
不经常用的方法为
- (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);
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 *[email protected]"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“==”来判断两个字符串时，实际上是判断地址是否相同
下面三个初始化语句的都是在常量区创建的
NSString *[email protected]"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 *[email protected]"我7";
stringwithcapacity 用来初始化NSMutableString
2、字符串的比较
compare、isEqualToString ：用来做比较
if([str isEqualToString:str2])
{
NSLog(@"They are the same");
}
/*
* 不区分大小写 compare options
*/
NSString *[email protected]"Block";
NSString *[email protected]"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实现将字符串分割为数组
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、判断是否有前缀
hasprefix. hasSuffix: 用来判断是否有前后缀
NSString *[email protected]"draft-hello.mov";
NSString *[email protected]"draft";
NSString *[email protected]"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 执行删除操作
*/
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; //开始位置
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、改变大小写
NSString *[email protected]"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的详解
NSArray有两个限制，首先，只能存储objective c的对象，不能存储c语言的基本语言类型，第二，不能包含nil对象
NSArray的用法：
1、初始化
NSArray *firstArray=[[NSArray alloc] initWithObjects:@"one",@"two",@"three", nil];
NSArray *secondArray=[NSArray arrayWithArray:firstArray];
2、获取元素个数和访问
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、判断是否包含字符串
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是可变的，NSArray是不可变的
6、基本的增删改
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，我们需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