我說常說v這個變量時知市，表示它是在棧里。
我們說v這個對象活孩，表示是v這個變量指向的對象物遇，但凡是指向的某個對象，都是在堆里憾儒。
字符串的一些常用方法
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
#if 0
NSString *str = @"hello world";
NSString *str2 = @"hello world_";
// str2 = str;
NSLog(@"str = %p",str);
NSLog(@"str2 = %p",str2);
NSString *s1 = @"hello world";
s1 = @"hello welcome";
#endif
NSString *str = @"hello world welcome to here";
//從下標0位打印到10止
NSString *subString = [str substringWithRange:NSMakeRange(0, 10)];
NSLog(@"subString = %@",subString);
//從下標第6位打印到結束
subString = [str substringFromIndex:6];
NSLog(@"subString = %@",subString);
//打印到第6位結束
subString = [str substringToIndex:6];
NSLog(@"subString = %@",subString);
#if 0
NSString *str1 = @"hello world";
NSString *str2 = @"hello world_";
if(str1 == str2){
NSLog(@"==");
}
#endif
#if 0
NSString *url = @"http://xxx.xxx.com";
//打印conrains包含的
if([url containsString:@"xxx"]){
NSLog(@"xxx");
}
//打印以這個結尾的
if([url hasSuffix:@"com"]){
NSLog(@"com");
}
//打印以這個開頭的
if([url hasPrefix:@"http"]){
NSLog(@"http");
}
#endif
NSRange range = [str rangeOfString:@"welcomp"];
NSLog(@"%ld",range.location);
if(range.location == NSNotFound){
}
//拼接地址
NSString *basePath = @"base";
//不會自動生成 / 符號
NSString *finalPath = [basePath stringByAppendingString:@"/Documents"];
//自動生成 / 符號
[basePath stringByAppendingPathComponent:@"Documents"];
//整數(shù)轉化為字符串
NSString *numStr = @"55";
numStr.integerValue;
NSInteger a = 55;
[NSString stringWithFormat:@"%ld",a];
//全部都轉換為小寫
NSString *name = @"ZhangSAN";
NSLog(@"name = %@",[name lowercaseString]);
//把數(shù)據(jù)轉換成UTF-8
NSData *data = [@"hello world" dataUsingEncoding:NSUTF8StringEncoding];
//將字符串轉化為數(shù)組
NSArray *arr = [str componentsSeparatedByString:@"world"];
NSLog(@"arr = %@",arr);
//打印的zhangsan這個名字前面有很多的空格询兴，空格是占用空間的。
NSString *userName = @" zhangsan";
NSLog(@"userName = %@",userName);
//這個方法是把多余的空格都去掉起趾。
NSString *finalUserName = [userName stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
NSLog(@"finalUserName = %@",finalUserName);
//把特定的字符都改寫成我們需要的字符诗舰，讓某些內(nèi)容不顯示出來。比如說把world阳掐，改寫成*號
NSString *secrStr = [str stringByReplacingOccurrencesOfString:@"world" withString:@"*"];
//把某個地址或者網(wǎng)址的文章始衅，讀取到文件里。
NSString *contents = [NSString stringWithContentsOfFile:@"--filePath--" encoding:NSUTF8StringEncoding error:nil];
//把某個地址或者網(wǎng)站的文章缭保，寫入到文件里。
[@"contetns" writeToFile:@"--target path" atomically:YES encoding:NSUTF8StringEncoding error:nil];
}
@end
