iOS常用知识点总结一

• 1、iOS子线程更新UI到主线程的三种方法
• 2、给self.view画一个类似self.layer.border的虚线边框
• 3、iOS画小于1px的细线
• 4、iOS 设置行距，并且计算有行距的文本高度
• 5、iOS NSData 转 Byte
• 6、PCH 绝对路径格式与相对路径
• 7、mac系统如何显示或者隐藏隐形的文件夹
• 8、Byte、char、NSData、NSString 相互转换
• 9、NSMutableData 的拼接、删除、插入

1、iOS子线程更新UI到主线程的三种方法

// 1.NSThread
[self performSelectorOnMainThread:@selector(updateUI) withObject:nil waitUntilDone:NO];
- (void)updateUI {    
// UI更新代码    
self.alert.text = @"Thanks!";
}
// 2.NSOperationQueue
[[NSOperationQueue mainQueue] addOperationWithBlock:^{  
  // UI更新代码    self.alert.text = @"Thanks!";    
}];
// 3.GCD
dispatch_sync(dispatch_get_main_queue(), ^{   
// UI更新代码   
self.alert.text = @"Thanks!";
 });

2、给self.view画一个类似self.layer.border的虚线边框

// 给self.view画一个类似self.layer.border的虚线边框
CAShapeLayer *border = [CAShapeLayer layer];
border.strokeColor = SLColorLine.CGColor;
border.fillColor = nil;
border.path = [UIBezierPath bezierPathWithRect:self.bounds].CGPath;
border.frame = self.bounds;
border.lineWidth = 1.f;
border.lineCap = @"square";
border.lineDashPattern = @[@4, @2];
[self.layer addSublayer:border];

3、iOS画小于1px的细线

CALayer *layer = view.layer;
layer.borderColor = [UIColor whiteColor].CGColor;
layer.borderWidth = (1.0 / [UIScreen mainScreen].scale / 2);

4、iOS 设置行距，并且计算有行距的文本高度

[text addAttribute:NSFontAttributeName value:[UIFont systemFontOfSize:16] range:NSMakeRange(0, text.length)];
 NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
[paragraphStyle setLineSpacing:5];//调整行间距
[text addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:NSMakeRange(0, [text length])];
[self.topicDeatil.article.content boundingRectWithSize:maxSize options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName : [UIFont systemFontOfSize:16]  ,NSParagraphStyleAttributeName : paragraphStyle} context:nil].size.height ;

5、iOS NSData 转 Byte

在iOS中NSData转Byte，见到最多的NSData转Byte的就是
    NSString *string = @"123456";
    NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];
    Byte *testByte = (Byte *)[data bytes];

但是这种方法常常是不可行的，这时候就要换下面的方法了，
    NSString *codeKey = @"123456";
    NSData *codeKeyData =  [codeKey dataUsingEncoding:NSUTF8StringEncoding];
    Byte codeKeyByteAry[codeKeyData.length];
    for (int i = 0 ; i < codeKeyData.length; i++) {
        NSData *idata = [codeKeyData subdataWithRange:NSMakeRange(i, 1)];
        codeKeyByteAry[i] =((Byte*)[idata bytes])[0];
    }

6、PCH 绝对路径格式与相对路径

PCH 绝对路径格式：/Users/wan/Desktop/项目名/项目名/PrefixHeader.pch，
      转化为相对路径，如下格式$(SRCROOT)/项目名/PrefixHeader.pch

7、mac系统如何显示或者隐藏隐形的文件夹

一:显示或者隐藏整个系统的隐形文件夹
   显示Mac隐藏文件的命令：defaults write com.apple.finder AppleShowAllFiles -bool true
   隐藏Mac隐藏文件的命令：defaults write com.apple.finder AppleShowAllFiles -bool false
二:显示或者隐藏某个目录下的隐形文件夹
   显示Mac隐藏文件的命令：defaults write com.apple.finder AppleShowAllFiles YES
   隐藏Mac隐藏文件的命令：defaults write com.apple.finder AppleShowAllFiles NO

8、Byte、char、NSData、NSString 相互转换

//1.1、NSData --> Byte
  NSString *testString = @"1234567890";
  NSData *testData = [testString dataUsingEncoding: NSUTF8StringEncoding];
  Byte *DataByte = (Byte *)[testData bytes];
   
//1.2、Byte --> NSData
  Byte byte[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23};
  NSData *Bytedata = [[NSData alloc] initWithBytes:byte length:24];
  NSInteger byteLength2 = sizeof(byte2);
  NSLog(@"字节长度_byteLength2= %zd",byteLength2);//byteLength2= 24
  NSLog(@"---<2.2>testByte: %s", DataByte);
  NSLog(@"---<2.2>Bytedata: %@\n ", Bytedata);

//2.1、 NSString 转化为 char*
  NSString *strr = @"Test转化123";
    const char * charA = [strr UTF8String];
  NSLog(@"charA = %s",charA);

//2.2、char* 转化为 NSString
  NSString *charToString = [NSString stringWithUTF8String:charA];
  NSLog(@"charToString= %@ \n ",charToString);

//3.1、：NSString --> NSData
    NSString * str1 = @"hello, world!";
    NSData * data = [str1 dataUsingEncoding:NSUTF8StringEncoding];
 
//3.2、NSData --> NSString
    NSString * dataString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"---<2.1>data.bytes: %s", data.bytes);
    NSLog(@"---<2.1>dataString: %@\n ", dataString);

9、NSMutableData 的拼接、删除、插入

    NSData *strData = [@"testdata" dataUsingEncoding:NSUTF8StringEncoding];
    NSMutableData *data = [NSMutableData data];

    [data appendData:strData];
    NSLog(@"data length= %ld",data.length);
    
    // delete
    [data replaceBytesInRange:NSMakeRange(0, 4) withBytes:NULL length:0];
    NSLog(@"data length= %ld",data.length);
    
    // insert
    [data replaceBytesInRange:NSMakeRange(0, 0) withBytes:strData.bytes length:strData.length];
    NSLog(@"data length= %ld",data.length);    
}