iOS中的常用基础小知识

1 随机数的使用

        头文件的引用

        #import <time.h>

        #import <mach/mach_time.h>

        srandom()的使用

        srandom((unsigned)(mach_absolute_time() & 0xFFFFFFFF));

        直接使用 random() 来调用随机数

iOS开发取随机数肯定会遇到的，暂时小结一下，好像有个arc4random(),所以假如你想取80到100的随机数，就可以写成intrandomNumber = arc4random() 

+80

int index = arc4random() % 6 +1;就是1到6的随机数了。

还有很多其它的取随机数的方法，论坛上也经常讨论

有网友问怎么生成不重复的随机数，说是生成一个随机种子如：
srand(time(NULL));rand() %1000;
还有一个这样的函数round(random()+10);取到的是10~24之间的数，但是是个伪随机数

怎么获得0到1之间的随机数，不包括0和1

思路是：求1--100之间的随机数就可以了然后/100

srand(time(0)); 
(float)(rand() % 100) /100;

(float)(1+arc4random()�)/100

总结：随机数最好使用arc4random，因为使用random()必须手动设置随机种子srandom(time(NULL));否则产生的就是伪随机数。

网友有个这样的想法：

   NSArray *temp = [NSArrayarrayWithObjects:@"1",@"2", @"3",@"4", @"5",@"6", nil];

   NSMutableArray *tempArray = [[NSMutableArrayalloc]initWithArray:temp];

      NSMutableArray*resultArray = [[NSMutableArrayalloc]init];

   int i;

   int count = temp.count;

   for (i =0; i < count; i ++) {

      int index =arc4random() % (count - i);

       [resultArray addObject:[tempArrayobjectAtIndex:index]];

       [tempArray removeObjectAtIndex:index];

    }

    [tempArrayrelease];

      NSLog(@"resultArray is %@",resultArray);

resultArray里面每个object的intValue就是你要的不重复随机数了

2 在UIImageView 中旋转图像

        float rotateAngle = M_PI;

        CGAffineTransform transform =CGAffineTransformMakeRotation(rotateAngle);

        imageView.transform = transform;

       

        以上代码旋转imageView, 角度为rotateAngle, 方向可以自己测试哦！

3 在Quartz中如何设置旋转点

        UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"bg.png"]];

        imageView.layer.anchorPoint = CGPointMake(0.5, 1.0);

        这个是把旋转点设置为底部中间。记住是在QuartzCore.framework中才得到支持。

4 创建.plist文件并存储

        NSString *errorDesc;  //用来存放错误信息

        NSMutableDictionary *rootObj = [NSMutableDictionary dictionaryWithCapacity:4]; //NSDictionary, NSData等文件可以直接转化为plist文件

        NSDictionary *innerDict;

        NSString *name;

        Player *player;

        NSInteger saveIndex;

    

        for(int i = 0; i < [playerArray count]; i++) {

              player = nil;

              player = [playerArray objectAtIndex:i];

              if(player == nil)

                     break; 

              name = player.playerName;// This "Player1" denotes the player name could also be the computer name

              innerDict = [self getAllNodeInfoToDictionary:player];

              [rootObj setObject:innerDict forKey:name]; // This "Player1" denotes the person who start this game

        }

        player = nil;

        NSData *plistData = [NSPropertyListSerialization dataFromPropertyList:(id)rootObj format:NSPropertyListXMLFormat_v1_0 errorDescription:&errorDesc];

        红色部分可以忽略，只是给rootObj添加一点内容。这个plistData为创建好的plist文件，用其writeToFile方法就可以写成文件。下面是代码：

        

        

        NSString *documentsPath = [self getDocumentsDirectory]; 

        NSString *savePath = [documentsPath stringByAppendingPathComponent:@"save.plist"];

    

        

        if (plistData) {

                [plistData writeToFile:savePath atomically:YES];

         }

         else {

                NSLog(errorDesc);

                [errorDesc release];

        }

        - (NSString *)getDocumentsDirectory {  

                NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);  

                return [paths objectAtIndex:0];  

        } 

4 读取plist文件并转化为NSDictionary

        NSString *documentsPath = [self getDocumentsDirectory];

        NSString *fullPath = [documentsPath stringByAppendingPathComponent:@"save.plist"];

        NSMutableDictionary* plistDict = [[NSMutableDictionary alloc] initWithContentsOfFile:fullPath];

5 读取一般性文档文件

        NSString *tmp;

        NSArray *lines;

        lines = [[NSString    stringWithContentsOfFile:@"testFileReadLines.txt"] 

                       componentsSeparatedByString:@"\n"];

    

         NSEnumerator *nse = [lines objectEnumerator];

    

         // 读取<>里的内容

         while(tmp = [nse nextObject]) {

                  NSString *stringBetweenBrackets = nil;

                  NSScanner *scanner = [NSScanner scannerWithString:tmp];

                  [scanner scanUpToString:@"<" intoString:nil];

                  [scanner scanString:@"<" intoString:nil];

                  [scanner scanUpToString:@">" intoString:&stringBetweenBrackets];

                  NSLog([stringBetweenBrackets description]);

          }

对于读写文件，还有补充，暂时到此。随机数和文件读写在游戏开发中经常用到。所以把部分内容放在这，以便和大家分享，也当记录，便于查找。

6 隐藏NavigationBar

[self.navigationController setNavigationBarHidden:YES animated:YES];

在想隐藏的ViewController中使用就可以了。