OC笔记

1. NSString 常用方法

 //字符串末尾拼接字符串
 NSString *newStr = [string1 stringByAppendingString:string2];
 
 //字符串成员的引用
 [string characterAtIndex:1]

 //比较两个字符串是否完全相同
 BOOL bl = [string1 isEqualToString:string2];

 //比较两个字符串的大小 
 NSComparisonResult result = [string1 compare:string2]; 
         NSOrderedAscending: string1 < string2
         NSOrderedSame: string1 == string2
         NSOrderedDescending: string1 > string2
   
 //忽略大小写的比较
 NSComparisonResult result = [string1 caseInsensitiveCompare:string2];

 //字符串中查找子串
 NSRange range = [string rangeOfString:@"substring"];

 //判断是否包含某个前缀
 BOOL bl = [str hasPrefix:@"txt"];

 //判断是否包含某个后缀
 BOOL bl = [str hasSuffix:@"txt"];

 //字符串转数字
 [string intValue]

 //将字符串中的小写字母转换成大写字母
 [string uppercaseString]

 //将字符串中的字母转换成小写字母
 [string lowercaseString]

 //首字母转大写
 [string capitalizedString]

 //字符串的提取：从某个位置开始提取，一直到字符串的末尾
 NSString *subFrom = [string substringFromIndex:0];
 //从字符串的开始提取到某个位置结束
 NSString *subTo = [string substringToIndex:[string length]];

#pragma mark -NSMutableString
 //字符串末尾拼接字符串
 [mutableString1 appendString:@"string"];

 //插入字符串
 [mutableString insertString:@"string" atIndex:3];

 //删除字符串
 NSRange range = {19, 3};
 [mutableString deleteCharactersInRange:range];

 //修改整个字符串
 [mutableString setString:@"modified”];

2. NSArray 常用方法

//数组成员的引用
[array objectAtIndex:0]

 //根据对象找索引
 [array indexOfObject:@"object"]

 //判断某个元素是否在数组中
 [array containsObject:@"object"]

 //获取数组中最后一个元素
 [array lastObject]

 //将字符串进行切割
 NSArray *array = [string componentsSeparatedByString:@"$"];

 //按照字符集进行切割
 NSArray *array = [string componentsSeparatedByCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"$#@&"]];

 //将数组每个元素用空格拼接成字符串
 NSString *stringFromArray = [arrayFromString componentsJoinedByString:@" "];

#pragma mark -NSMutableArray
 //数组末尾增加一个元素
 [mutableArray addObject:@"object"];

 //数组的末尾增加一个数组
 [mutableArray addObjectsFromArray:array];
 
 //数组中插入一个元素
 [mutableArray insertObject:@"object" atIndex:2];

 //删除数组中的指定元素,有多少删多少
 [mutableArray removeObject:@"object"];
 
 //删除指定下标的元素
 [mutableArray removeObjectAtIndex:2];

 //删除指定范围内的元素
 NSRange range = {0, 2};
 [mutableArray removeObjectsInRange:range];

 //删除最后一个元素
 [mutableArray removeLastObject];

 //删除整个数组
 [mutableArray removeAllObjects];

 //数组成员的替换
 [mutableArray replaceObjectAtIndex:0 withObject:@"object"];

 //数组成员的交换，参数是交换的两个成员下标
 [mutableArray exchangeObjectAtIndex:1 withObjectAtIndex:2];

3. NSDictionary 常用方法

 //字典的创建
 NSDictionary *dictionary = [[NSDictionary alloc] initWithObjectsAndKeys:
                       @"value1", @"key1",
                       @"value2", @"key2", nil];

 //字典键值对的个数
 [dictionary count]

 //根据key找value
 [dictionary objectForKey:@"key"]
 
 //获取字典中所有的key值
 NSArray *allKeys = [dictionary allKeys];

#pragma mark -NSMutableDictionary
 //添加整个字典到可变字典中
 [mutableDictionary addEntriesFromDictionary:dic];

 /* 添加或修改键值对:
  如果字典中存在key，那就就修该对应的value值，
  如果字典中不存在key, 那就进行添加键值对 */
 [mutableDictionary setObject:@"value" forKey:@"key"]

 //根据key 删除键值对
 [mutableDictionary removeObjectForKey:@"key"];

 //删除所有的键值对
 [mutableDic removeAllObjects];

 //修改整个字典
 [mutabelDic setDictionary:dic];

4. 简单的数据持久化

 //NSData可以存储图片、声音等二进制数据
 //dataToString
 NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];
 NSString *strFormData = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

//plist文件的创建与读取
//将该字典写入到list文件中，并读取plist文件中内容
void dictionaryToPlist(void) {

    NSString *pathDesktop = @"/Users/mac/Desktop"; 
    NSArray *array1 = [NSArray arrayWithObjects:@"one", @"two", nil];
    NSArray *array2 = [NSArray arrayWithObjects:@"beijing", @"shanghai", nil];
    
    NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:
                                array1, @"key1",
                                array2, @"key2", nil];
    
    [dictionary writeToFile:[pathDesktop stringByAppendingString:@"/1.plist"] atomically:YES];//持久化字典对象 (写入到plist文件中)
    
    NSDictionary *dicFromPlist = [NSDictionary dictionaryWithContentsOfFile:[pathDesktop stringByAppendingString:@"/1.plist"]];// 读取plist内容
    NSLog(@"%@", dicFromPlist);
}