iOS基础积累

识别设备是否为pad

[[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad

判断设备方向为纵向

UIInterfaceOrientationIsPortrait() YES

NSUserDefault是存储在本地磁盘上的，相当于ini文件

[[NSUserDefaults standardUserDefaults] setObject:perid forKey:PerIdKey];

使用GCD实现多线程操作

dispatch_async(dispatch_get_global_queue(0, 0), ^{

NSArray* array = [myMngObjCtx getLastLogin];

//sub complete turn to main 子线程要自己管理内存释放

dispatch_async(dispatch_get_main_queue(), ^{

for ( NSManagedObject* obj in array) {

[self.userNameEd setText:[obj valueForKey:@"username"]];

}

});//main

}); //dispatch async

按钮图标总是显示为默认色实心圆，这样改代码

selImage =[selImage imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];

如果是在cell里的button，则需要设置不透明

self.OrganNext.opaque = YES;

去除表格视图的表格线

self.tableView.separatorStyle = UITableViewCellSeparatorStyleNone;

服务端返回json的时候带有“null”

[myinfo.signature isKindOfClass:[NSNull class]]

如果写＝＝［NSNull null］判断会有警告

从storyboard中读取资源生成controller

UIStoryboard* story = [UIStoryboard storyboardWithName:@"Main" bundle:nil];

ViewController* login = [story instantiateViewControllerWithIdentifier:@"rlogin"];

获取app下document文件夹

[[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];

建立model、coordinate、sqlite文件关联

NSPersistentStoreCoordinator* coordin = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:aManaObjModel];

[coordin addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:nil error:&err];

数据库删除

[aManaObjCtx deleteObject:managedobject];

BOOL ret = [aManaObjCtx save:&err];

数据库查询

NSEntityDescription* desc = [NSEntityDescription entityForName:@"Login" inManagedObjectContext:aManaObjCtx];

NSFetchRequest* req = [[NSFetchRequest alloc] initWithEntityName:@"Login"];

[req setEntity:desc];

NSSortDescriptor *sort=[[NSSortDescriptor alloc]initWithKey:@"lasttime" ascending:NO];

NSArray* sortArray = @[sort];

[req setSortDescriptors:sortArray];

NSPredicate* pre = [NSPredicate predicateWithFormat:@"personid = %@",personid];

[req setPredicate:pre];

NSError* err = nil;

NSArray* result = [aManaObjCtx executeFetchRequest:req error:&err];

alloc方法

类方法alloc申请到内存后，还顺便把内存全部置为0，这样就不必担心未初始化数据导致各种随机奇怪问题（比如C++语言会出现的问题）但是仍然必须调用对象的init方法（及其变体）

xml文档解析

-(BOOL)parser:(NSString*)string

{

//系统自带的

NSXMLParser *par = [[NSXMLParser alloc] initWithData:[string dataUsingEncoding:NSUTF8StringEncoding]];

[par setDelegate:self];//设置NSXMLParser对象的解析方法代理

return [par parse];//调用代理解析NSXMLParser对象，看解析是否成功

}

#pragma mark xmlparser

//step 1 :准备解析

- (void)parserDidStartDocument:(NSXMLParser *)parser

{

//start node

NSLog(@"%@",NSStringFromSelector(_cmd) );

}

//step 2：准备解析节点命名空间、限定名

(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)

elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary*)attributeDict

{

NSLog(@"ele:%@ \n nsp:%@ \n qN:%@ \n attr:%@",elementName,

namespaceURI,qName,[attributeDict description] );

}

//step 3:获取一个节点里的内容；可能会调用多次！接收时使用append

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string

{

//content

NSLog(@"%@",string );

}

//step 4 ：解析完当前节点

(void)parser:(NSXMLParser *)parser didEndElement:(NSString *)

elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName

{

NSLog(@"%@ end",elementName );

}

//step 5；解析结束

- (void)parserDidEndDocument:(NSXMLParser *)parser

{

//document end

NSLog(@"%@",NSStringFromSelector(_cmd) );

}

//获取cdata块数据

- (void)parser:(NSXMLParser *)parser foundCDATA:(NSData *)CDATABlock

{

NSLog(@"%@",CDATABlock.description );

}

把数组中元素用指定间隔符合成字符串

[array componentsJoinedByString:@”-”]

指定分隔符分割字符串到数组

[title componentsSeparatedByString:@"-"]

从文件读取内容得到字符串

[[NSString alloc] initWithContentsOfFile:@"a.txt" encoding:NSUTF8StringEncoding error:nil];

测试一个类是否有某个方法实现，一般用于接口类

[model respondsToSelector:@selector(selector)];

KVC快速运算，成员变量名不要打错，返回值为对象

NSNumber* count = [garage valueForKeyPath:@"cars.@count" ];

NSNumber* sum = [garage valueForKeyPath:@"cars.@sum.millage"];

NSNumber* avg = [garage valueForKeyPath:@"cars.@avg.millage"];

block代码块

app启动