一、NSString的创建
1 int main(int argc, const char * argv[])
2 {
3
4 @autoreleasepool {
5
6 //这种方式不需要release
7 NSString *s1 = @"this is a string";
8 NSLog(@"s1=%@", s1);
9
10 //这种方式需要release
11 NSString *s2 = [[NSString alloc] init];
12 s2 = @"this is a string";
13 NSLog(@"s2=%@", s2);
14 [s2 release];
15
16 //这种方式需要release
17 NSString *s3 = [[NSString alloc] initWithString:@"this is a string"];
18 NSLog(@"s3=%@", s3);
19 [s3 release];
20 //这种方式不需要release
21 s3 = [NSString stringWithString:@"this is a string"];
22 NSLog(@"s3=%@", s3);
23
24 //这种方式需要release
25 NSString *s4 = [[NSString alloc] initWithUTF8String:"this is a string"];
26 NSLog(@"s4=%@", s4);
27 [s4 release];
28 //这种方式不需要release
29 s4 = [NSString stringWithUTF8String:"this is a string"];
30 NSLog(@"s4=%@", s4);
31
32 //这种方式需要release
33 NSString *s5 = [[NSString alloc] initWithFormat:@"my age is %i and height is %.2f", 18, 1.7f];
34 NSLog(@"s5=%@", s5);
35 [s5 release];
36 //这种方式不需要release
37 s5 = [NSString stringWithFormat:@"my age is %i and height is %.2f", 18, 1.7f];
38 NSLog(@"s5=%@", s5);
39
40 }
41 return 0;
42 }
二、NSString的常用方法
1 int main(int argc, const char * argv[])
2 {
3
4 @autoreleasepool {
5
6 NSString *s1 = @"This is a String";
7 // 转大写
8 NSLog(@"%@", [s1 uppercaseString]); //THIS IS A STRING
9 // 转小写
10 NSLog(@"%@", [s1 lowercaseString]); //this is a string
11 // 每个单词的首字母转大写
12 NSLog(@"%@", [s1 capitalizedString]); //This Is A String
13
14 // 比较两个字符串的内容是否相同
15 BOOL r1 = [@"abc" isEqualToString:@"Abc"];
16 NSLog(@"%i", r1); //0
17
18 // 逐个字符进行比较大小
19 NSComparisonResult r2 = [@"abc" compare:@"Abc"];
20 if (r2==NSOrderedSame) {
21 NSLog(@"两个字符串的内容相同");
22 } else if (r2==NSOrderedAscending) {
23 NSLog(@"右边 > 左边");
24 } else if (r2==NSOrderedDescending) {
25 NSLog(@"右边 < 左边");
26 }
27
28 // 是否以This开头
29 BOOL r3 = [s1 hasPrefix:@"This"];
30 NSLog(@"%i", r3); //1
31 // 是否以String结尾
32 BOOL r4 = [s1 hasSuffix:@"String"];
33 NSLog(@"%i", r4); //1
34
35 // 查找is在s1中的位置，
36 NSRange r5 = [s1 rangeOfString:@"is"];
37 if (r5.location == NSNotFound) {
38 NSLog(@"找不到");
39 } else {
40 NSLog(@"%@", NSStringFromRange(r5)); //{2, 2}
41 }
42
43 // 从尾部查找is在s1中的位置，
44 NSRange r6 = [s1 rangeOfString:@"is" options:NSBackwardsSearch];
45 if (r6.location == NSNotFound) {
46 NSLog(@"找不到");
47 } else {
48 NSLog(@"%@", NSStringFromRange(r6)); //{5, 2}
49 }
50
51 // 从索引3开始截取到末尾
52 NSLog(@"%@", [@"123456" substringFromIndex:3]); //456
53 // 从头部截取到索引3之前
54 NSLog(@"%@", [@"123456" substringToIndex:3]); //123
55 // 指定范围截取
56 NSLog(@"%@", [@"123456" substringWithRange:NSMakeRange(2, 3)]); //345
57
58 // 分隔字符串
59 NSArray *arr = [@"1,2,3,4,5" componentsSeparatedByString:@","];
60 NSLog(@"%@", arr[2]); //3
61
62 // 字符串长度
63 NSLog(@"%zi", [@"abc" length]); //3
64 // 转为int
65 NSLog(@"%i", [@"12" intValue]);
66
67 }
68 return 0;
69 }
三、从文件中读取文本
1 int main(int argc, const char * argv[])
2 {
3
4 @autoreleasepool {
5
6 NSString *path = @"/Users/Lane/Desktop/test.txt";
7
8 NSError *error;
9
10 NSString *s1 = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:&error];
11
12 if (error) {
13 NSLog(@"文件读取失败: %@", error);
14 } else {
15 NSLog(@"%@", s1);
16 }
17
18
19 }
20 return 0;
21 }
四、从URL中读取文本
1 int main(int argc, const char * argv[])
2 {
3
4 @autoreleasepool {
5
6 NSURL *url = [NSURL URLWithString:@"http://www.baidu.com"];
7
8 NSError *error;
9
10 NSString *s1 = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&error];
11
12 if (error) {
13 NSLog(@"URL读取失败: %@", error);
14 } else {
15 NSLog(@"%@", s1);
16 }
17
18
19 }
20 return 0;
21 }
五、写入文本文件
1 int main(int argc, const char * argv[])
2 {
3
4 @autoreleasepool {
5
6 NSString *path = @"/Users/Lane/Desktop/test2.txt";
7
8 NSError *error;
9
10 NSString *s1 = @"123456";
11 [s1 writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:&error];
12
13 if (error) {
14 NSLog(@"文件写入失败: %@", error);
15 } else {
16 NSLog(@"文件写入成功");
17 }
18
19
20 }
21 return 0;
22 }
