1、訪問私有屬性
originalURL 是 imageMessage.m 中的屬性
/// 通過 valueForKey 或 valueForKeyPath 訪問
self.originalPath = [imageMessage valueForKeyPath:@"thumbnailURL"];
/// 通過 runtime 訪問
Ivar ivar = class_getInstanceVariable([ImageMessage class], "_thumbnailURL");
id content = object_getIvar(imageMessage, ivar);
2、訪問 bundle 中的 json 文件
NSString *path = [[NSBundle mainBundle] pathForResource:@"test.json" ofType:nil];
NSData *jsonData = [NSData dataWithContentsOfFile:path];
NSArray *array = [NSJSONSerialization JSONObjectWithData:jsonData options:kNilOptions error:nil];
NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:jsonData options:kNilOptions error:nil];
3、隱藏導航欄返回標題
[[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(0, -60) forBarMetrics:UIBarMetricsDefault];
4、weak self
__weak typeof(self) weakSelf = self;
5、cell 內容超出邊界
cell.clipsToBounds = YES;
6、string to int
- (int)convertToInt:(NSString*)strtemp
{
NSStringEncoding enc = CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000);
NSData* da = [strtemp dataUsingEncoding:enc];
return [da length];
}
7、push viewController 時，隱藏 tabbar
[viewController setHidesBottomBarWhenPushed:YES];
8、在 view 的某些子視圖禁用 gesture
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
if ([touch.view isDescendantOfView:self.tableView]) {
return NO;
}
return YES;
}
9、讓 tableview 的 section 滾動
- (void) scrollViewDidScroll:(UIScrollView *)scrollView {
CGFloat sectionHeaderHeight = 30;
BOOL isUpSectionScrollToNavigation = scrollView.contentOffset.y <= sectionHeaderHeight && scrollView.contentOffset.y >= 0;
BOOL isDownSectionScrollOutNavigation = scrollView.contentOffset.y >= sectionHeaderHeight;
if (isUpSectionScrollToNavigation) {
scrollView.contentInset = UIEdgeInsetsMake(-scrollView.contentOffset.y, 0, 0, 0);
}else if (isDownSectionScrollOutNavigation){
scrollView.contentInset = UIEdgeInsetsMake(-sectionHeaderHeight, 0, 0, 0);
}
}
10、在 willDisplayCell:forRowAtIndexPath 設置 字體和顏色
11、從像素px轉換為ios的點陣pt
+ (CGFloat)convertPixlToPoint:(CGFloat)px{
CGFloat standardPt = px/2.0;
if (iphone5) {
standardPt = (iphone5W/iphone6W)*standardPt;
}else if(iphone6){
}else if(iphone6plus){
standardPt = (iphone6plusW/iphone6W)*standardPt;
}else;
return standardPt;
}
12、指定集合中的數據類型
NSArray<NSString *> *strings = @[@"ha0", @"ha1"];
NSDictionary<NSString *, NSNumber *> *mapping = @{@"a": @1, @"b": @2};
13、Xcode 插件失效
find ~/Library/Application\ Support/Developer/Shared/Xcode/Plug-ins -name Info.plist -maxdepth 3 | xargs -I{} defaults write {} DVTPlugInCompatibilityUUIDs -array-add `defaults read /Applications/Xcode.app/Contents/Info.plist DVTPlugInCompatibilityUUID`
14、當前語言
#define CURRENTLANGUAGE ([[NSLocale preferredLanguages] objectAtIndex:0])
15、tableview 滑動到頂部
[tableview scrollRectToVisible:CGRectMake(0, 0, 1, 1) animated:NO];
16、image 合并
UIGraphicsBeginImageContext(size);
[image1 drawInRect:CGRectMake(0, 0, image1.size.width, size.height)];
[image2 drawInRect:CGRectMake(image1.size.width, 0, image2.size.width, size.height)];
UIImage *togetherImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
17、系統自帶滑動返回
self.navigationController.interactivePopGestureRecognizer.delegate = self;
18、檢測 string 中的鏈接
NSDataDetector* detector = [NSDataDetector dataDetectorWithTypes:NSTextCheckingTypeLink error:nil];
NSArray* matches = [detector matchesInString:attributedString.string options:0 range:NSMakeRange(0, [attributedString.string length])];
19、用 NSCache 作緩存
@property (strong, nonatomic) NSCache *photosCache; [self.photosCache objectForKey:photoName];
[self.photosCache setObject:thumbImage forKey:photoName];
20、array to string
NSString * result = [[array valueForKey:@"description"] componentsJoinedByString:@""];
21、使用 reveal 的配置
command alias reveal_load expr (Class)NSClassFromString(@"IBARevealLoader") == nil ? (void*)dlopen((char*)[(NSString*)[(NSBundle*)[NSBundle mainBundle] pathForResource:@"libReveal" ofType:@"dylib"] cStringUsingEncoding:0x4], 0x2) : ((void*)0)
22、關于圖片處理
蘋果對 JPEG 有硬編碼和硬解碼，保存成 JPEG 會大大縮減編碼解碼時間，也能減小文件體積。如果圖片不包含透明像素時，UIImageJPEGRepresentation(0.9) 是最佳的圖片保存方式，其次是 UIImagePNGRepresentation()。
23、Don’t call setNeedsDisplay unless the content of the view has really changed.
By overriding layoutSubviews, you can make your application much smoother during rotation and scrolling events
24、一些 sql
SELECT AGE FROM COMPANY WHERE EXISTS (SELECT AGE FROM COMPANY WHERE SALARY > 65000);
select coalesce(comm,0) from emp
select ename, job, deptno from emp where deptno in (10,20) and (ename like '%I%' or job like '%ER')
select ename, job, sal from emp where deptno = 10 order by 3 desc //3與sal對應
select e.ename , d.loc from emp e inner join dept d on (e.deptno = d.deptno) where e.deptno = 10
select e.ename, e.empno, e.job, e.sal, e.deptno from emp e join v2 on(e.ename = v2.ename and e.job = v2.job and e.sal = v2.sal)
select deptno from dept except select deptno from emp //求差集
select d.* from dept d left outer join emp e on (d.deptno = e.deptno) where e.deptno is null //outer可選
update emp set sal = sal * 1.20 where empno in (select empno from emp_bonus)
//_匹配單個字符
（范圍內的數據）SELECT *FROM movies WHERE name BETWEEN 'A' AND 'J';
（與條件選擇）SELECT * FROM movies WHERE year BETWEEN 1990 AND 2000 AND genre = 'comedy';
（或條件選擇）SELECT * FROM movies WHERE genre = 'comedy' OR year < 1980;
（排序）SELECT * FROM movies ORDER BY imdb_rating DESC;
（選取前幾個）SELECT * FROM movies ORDER BY imdb_rating ASC LIMIT 3;
（計數）SELECT COUNT(*) FROM fake_apps;
（條件計數）SELECT COUNT(*) FROM fake_apps WHERE price = 0;
（分組計數）SELECT price ,COUNT(*) FROM fake_apps GROUP BY price;
（求和）SELECT SUM(downloads) FROM fake_apps;
（最大值）SELECT MAX(downloads) FROM fake_apps;
（最小值）SELECT MIN(downloads) FROM fake_apps;
（平均值）SELECT AVG(downloads) FROM fake_apps ;
（控制小數點）SELECT price , ROUND(AVG(downloads),2) FROM fake_apps GROUP BY price;
24、NSDateFormatter
G: 公元時代，例如 AD 公元
yy: 年的后 2 位
yyyy: 完整年
MM: 月，顯示為 1-12
MMM: 月，顯示為英文月份簡寫, 如 Jan
MMMM: 月，顯示為英文月份全稱，如 Janualy
dd: 日，2 位數表示，如 02
d: 日，1-2 位顯示，如 2
EEE: 簡寫星期幾，如 Sun
EEEE: 全寫星期幾，如 Sunday
aa: 上下午，AM/PM
H: 時，24 小時制，0-23
K：時，12 小時制，0-11
m: 分，1-2 位
mm: 分，2 位
s: 秒，1-2 位
ss: 秒，2 位
S: 毫秒
Z：GMT 