一個iOS開發人員必須掌握的66個知識點，你掌握了多少？

1. 不可變數組  轉變為可變數組 
聲明執行個體變數的數組  必須記得實現

對於遍曆數組找到對象後 如果還需要尋找 記得先結束 再尋找(return/break) NSArray * arr = @[@"人在囧途",@"煎餅俠",@"西遊記",];

NSMutableArray *  arr = [NSMutableArray arrayWithArray:arr]; 在數組中取資料的時候  需要通過尾碼 將數組中的對象轉化為數字類
p11. age   = [newArr[1] intValue ];

2.擷取字串長度 
NSString * str = nameLabel .text;
CGSize   size   = [str   sizeWithAttributes :@{ NSFontAttributeName : [UIFont systemFontOfSize:17]}];
此時即可得到   size .width   (字串的寬  即 字串長度)

3.將單獨的某個視圖上的視圖控制器的導航條隱藏 

-(void)viewDidAppear:(BOOL)animated{    [super viewDidAppear:animated == NO];    [self .navigationController setNavigationBarHidden:YES];}

4. 邊帽法 (展開圖片) 將某一像素點兒不斷地複製  其他像素點不變 展開之後不會是圖片變形

//第一種    [[UIImageView alloc] init].image = [[UIImage imageNamed:@"bubble.png"] stretchableImageWithLeftCapWidth:20 topCapHeight:20];    //第二種    UIImage * image =[UIImage imageNamed:@"7.jpg"];    [image resizableImageWithCapInsets:UIEdgeInsetsMake(0, image.size.width, 0, 0)];    [[UIImageView alloc] init].image = image;

5. 監聽系統發送的通知 

//  監聽鍵盤frame發生變化的通知  並可以通過鍵盤的屬性獲得對象    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(KeyboardWillChangeFrame:) name:UIKeyboardWillChangeFrameNotification object:nil];        - (void)KeyboardWillChangeFrame:(NSNotification *)noti {//        UIKeyboardAnimationCurveUserInfoKey = 7;//        UIKeyboardAnimationDurationUserInfoKey = "0.25";//        UIKeyboardBoundsUserInfoKey = "NSRect: {{0, 0}, {320, 216}}";//        UIKeyboardCenterBeginUserInfoKey = "NSPoint: {160, 588}";//        UIKeyboardCenterEndUserInfoKey = "NSPoint: {160, 372}";//        UIKeyboardFrameBeginUserInfoKey = "NSRect: {{0, 480}, {320, 216}}";//        UIKeyboardFrameChangedByUserInteraction = 0;//        UIKeyboardFrameEndUserInfoKey = "NSRect: {{0, 264}, {320, 216}}";                //一旦鍵盤發生改變的時候  _inputView  和  _tableView 的座標都要發生改變        //通過字典 擷取對象        NSDictionary * dic = noti .userInfo;                //擷取動畫時間長度        float time = [[dic objectForKey:UIKeyboardAnimationDurationUserInfoKey] floatValue];                //擷取動畫速率        int curve = [[dic objectForKey:UIKeyboardAnimationCurveUserInfoKey] intValue];                //擷取鍵盤座標        CGRect rect = [[dic objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];    }

6.通過字串繪製矩形  MAXFLOAT 無限

NSString * str = _chatArr[indexPath .row];CGRect rect = [str  boundingRectWithSize:CGSizeMake(200, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading attributes:@{NSFontAttributeName: [UIFont systemFontOfSize:15]} context:nil];

7.視圖層級切換 
關鍵點:
 [self .window exchangeSubviewAtIndex:0 withSubviewAtIndex:1];
1.   如果父視圖不可互動  那麼放在其上邊的子視圖也不可互動
2. 如果父視圖可以互動  那麼放在上邊的子視圖的可互動性由自己決定
關鍵詞 :   userInteractionEnabled
image . userInteractionEnabled   =   YES ;

8.位元據轉變類型 

字串轉變為位元據

NSString * str = @"girls"; NSData * data = [str dataUsingEncoding:NSUTF8StringEncoding];

位元據轉變為字串 NSString * str2 =[[NSString alloc]initWithData:data1 encoding:NSUTF8StringEncoding];

將圖片轉變為位元據

1.需要獲得圖片路徑 

NSString * imageViewPath =[[NSBundle mainBundle]pathForResource:@"18" ofType:@"jpg"];

NSData * data = [[NSData alloc]initWithContentsOfFile:imageViewPath];

2.直接將添加在工程中的圖片轉化為位元據類型

UIImage * image = [UIImage imageNamed:@"20.jpg"]; NSData   * data =  UIImageJPEGRepresentation (image,   1 );

將轉變為位元據的圖片轉變回圖片

方法1   可以直接調用 從路徑中取出圖片

 UIImage * image = [UIImage imageWithContentsOfFile:dataPath];

方法2 : 先將路徑中的位元據取出  然後 通過ImageWithData 屬性轉變為圖片類型

NSData * data = [NSData dataWithContentsOfFile:[self getFilePath:@"data.plist"]]; UIImage * image =[UIImage imageWithData:data];

9.如何刪除一個視圖上的所有子視圖  所有代碼  :

擷取視圖上存放的所有子視圖  遍曆數組 找到所有對象 找到 views

for (UIView * v in self.view.subviews) {    [v removeFromSuperview];}

10.將某個視圖放在最前邊
 [self .view bringSubviewToFront:_tableView];

11.頁面跳轉(需要找window)
// 找 window
 方法 1:

UIWindow * window =[[[UIApplication sharedApplication]delegate]window];window .rootViewController = aViewController;

 方法 2:

UIApplication * app = [UIApplication sharedApplication];AppDelegate * delegate = app .delegate;UIWindow * window = delegate .window ;window .rootViewController = aViewController;

1.   頁面翻轉

[UIView beginAnimations:nil context:nil];[UIView setAnimationDuration:1];[UIView setAnimationTransition:UIViewAnimationTransitionCurlUp forView:window cache:YES];[UIView commitAnimations];

2. 模態彈出  (present  展示     dismiss  消失 )

3. 導航控制器  (push  壓棧   pop  出棧 ) //通過導航控制器控制視圖切換的時候

1. 返回上一介面:  [ self   . navigationController   popViewControllerAnimated :