小知识: NS:NextStep CG:CoreGraphics
NSString:不可变字符串 NSMutableString:可变字符串
URL本地文件头: file:// URL网络文件头:http://
int main(int argc, const char * argv[]){
int age = 10;
1.字符串的创建
NSString *s1 = @"As god name";
NSString *s2 = [[NSString alloc] initWithString:@"欢迎学习OC"]; // 不常用
NSString *s3 = [[NSString alloc] initWithFormat:@"欢迎学习OC, age = %d", age]; // 不常用
NSString *s4 = [NSString stringWithFormat:@"欢迎学习OC, age = %d", age];
// C字符串 --> OC字符串
NSString *s5 = [[NSString alloc] initWithFormat:@"欢迎学习OC"];
// OC字符串 --> C字符串
const char *s5 = [s4 UTF8String];
// 从文件中读取字符串
NSString *s6 = [NSString stringWithContentsOfFile:@"/Users/apple/Desktop/one.txt" encoding:NSUTF8StringEncoding error:nil];
// URL字符串的读取
NSURL *url = [[NSURL alloc] initWithString:@"file:///Users/apple/Desktop/one.txt"]; // URL路径的创建
NSURL *url2 = [NSURL fileURLWithPath:@"/Users/apple/Desktop/one.txt"]; // URL路径的创建
// 从URL路径中读取字符串
NSString *s7 = [[NSString alloc] initWithContentsOfURL:url2 encoding:NSUTF8StringEncoding error:nil];
NSLog(@"%@", s7);
// 将字符串写入到文件中
NSString *s8 = @"欢迎学习OC";
NSURL *url3 = [[NSURL alloc] initWithString:@"file:///Users/apple/Desktop/three.txt"];
[s8 writeToFile:url3 atomically:YES encoding:NSUTF8StringEncoding error:nil];
// NSMutableString
NSMutableString *s10 = [NSMutableString stringWithFormat:@"欢迎学习OC"];
[s10 appendString:@" 欢迎学习ios开发"]; // 拼接内容到s1的后面
NSString *s11 = [NSString stringWithFormat:@"欢迎来到我的博客"];
NSString *s12 = [s2 stringByAppendString:@" and other..."]; // 在s11后添加字符串
return 0;
}