查看文档(API) (NSString)

查看文档(API) 

 

        OC的数据类型 

        NSInteger: 整型(32 = int, 64 = long) 

        CGFloat: 浮点型(32 = float, 64 = double)

        如何学习系统的类

        1.查看文档(API)

        a. 类的概况(overview)

        b. 类的继承关系(inherit)

        c. 创建对象的方法(init, 自定义初始化方法, 便利构造器)

        d. 找方法   

        NSString: 不可变字符串类(字符串一旦被创建, 就不能更改), 继承于NSObject

        创建字符串对象

 NSString *str1 = [NSString string];//空字符串
        NSLog(@"%@", str1);   
        NSString *str2 = @"iOS";//常量字符串
        NSLog(@"%@", str2);
        NSLog(@"%p", str2);

 NSString *str4 = [[NSString alloc]initWithFormat:@"Hello, %@", str2];
        NSLog(@"%@", str4);
        
        NSInteger a = 10, b = 5;
        //创建一个字符串, "10 + 5 = 15"
        NSString *str5 = [[NSString alloc]initWithFormat:@"%ld + %ld = %ld", a, b, a + b ];
        NSLog(@"%@", str5);
        
        //创建一个字符串, "10 + 5 = 105"
        NSString *str6 = [[NSString alloc]initWithFormat:@"%ld + %ld = %ld%ld", a, b, a, b];
        NSLog(@"%@", str6);

        //创建一个字符串, "5 + 10 = 510"
        NSString *str7 = [NSString stringWithFormat:@"%ld + %ld = %ld%ld", b, a, b, a];
        NSLog(@"%@", str7);

求字符串的长度

NSString *str8 = @"你问我爱你有多深?月亮代表我的心";
        NSUInteger length = [str8 length];
        NSLog(@"%lu", length);

获取子字符串"我爱你"

//NSRange range = {2, 3};
        NSString *str9 = [str8 substringWithRange:range];
        NSRange range1 = NSMakeRange(9, 2);
        NSString *str9 = [str8 substringWithRange:range1];
        
        NSString *str9 = [str8 substringWithRange:NSMakeRange(9, 2)];
        NSLog(@"%@", str9);

//"月亮代表我的心"
        NSString *str10 = [str8 substringFromIndex:9];
        NSLog(@"%@", str10);
        
        //"你问我爱你有多深"
        NSString *str11 = [str8 substringToIndex:8];
        NSLog(@"%@", str11);
        
        NSString *str12 = @"天再高又怎样";
        NSString *str13 = @"踮起脚尖就更靠近阳光";
        //"天再高又怎样踮起脚尖就更靠近阳光"
        NSString *str14 = [str12 stringByAppendingString:str13];
        NSLog(@"%@", str14);
        //"天再高又怎样, 踮起脚尖就更靠近阳光"
        NSString *str15 = [str12 stringByAppendingFormat:@", %@", str13];
        NSLog(@"%@", str15);
        
        NSString *str16 = [NSString stringWithFormat:@"%@, %@", str12, str13];
        NSLog(@"%@", str16);

字符串的替换

 NSString *str17 = @"微笑拥抱每一天, 做向日葵温暖的女子";
        NSString *str18 = [str17 stringByReplacingOccurrencesOfString:@"女子" withString:@"女汉子"];
        NSLog(@"%@", str18);
        
        NSString *str19 = @"baoshuang";
        NSString *str20 = @"wenbin";
        NSComparisonResult result = [str19 compare:str20];
        switch (result) {
            case NSOrderedAscending://右边大
                NSLog(@"%@ < %@", str19, str20);
                break;
            case NSOrderedSame://相等
                NSLog(@"%@ = %@", str19, str20);
                break;
            case NSOrderedDescending://左边大
                NSLog(@"%@ > %@", str19, str20);
                break;
            default:
                break;
        }

比较字符串是否相等

 NSString *str21 = @"NBA";
        NSString *str22 = @"CBA";
        
        BOOL isSame = [str21 isEqualToString:str22];
        if (isSame) {
            NSLog(@"相等");
        } else {
           NSLog(@"不相等");
        }

判断字符串是否以xxx开头

NSString *str23 = @"http://www.2048.com";
        BOOL flag = [str23 hasPrefix:@"http://"];
        if (flag) {
            NSLog(@"OK");
        }

判断字符串是否以xxx结尾

 NSString *str24 = @"guangen.png";
//        NSString *str25 = @"";
        //判断是否以png结尾, 如果是, 把png改为avi
        flag = [str24 hasSuffix:@".png"];
        if (flag) {
            NSString *str25 = [str24 stringByReplacingOccurrencesOfString:@"png" withString:@"avi"];
            NSLog(@"%@", str25);
        }
        
        NSString *str26 = @"I loVe you Not who yoU are, but for who I am before you";

字符串改成小写

NSString *str27 = [str26 lowercaseString];
        NSLog(@"%@", str27);

改成大写

NSString *str28 = [str26 uppercaseString];
        NSLog(@"%@", str28);

首字母大写

NSString *str29 = [str26 capitalizedString];
        NSLog(@"%@", str29);

字符串类型转换为基本类型(int, long, float, double)

NSString *str30 = @"123.456";
        int number1 = [str30 intValue];
        NSLog(@"%d", number1);
        
        NSInteger number2 = [str30 integerValue];
        NSLog(@"%ld", number2);
        
        float number3 = [str30 floatValue];
        NSLog(@"%f", number3);
        
        double number4 = [str30 doubleValue];
        NSLog(@"%lf", number4);

转换回去

NSString *str31 = [NSString stringWithFormat:@"%d", number1];
        NSLog(@"%@", str31);

        NSMutableString, 可变字符串类(可以被编辑), 继承于NSString

 创建可变字符串

NSMutableString *string = [[NSMutableString alloc]initWithCapacity:0];
        NSLog(@"%@", string);

赋值

 [string setString:@"人生没有彩排, 每天都是现场直播"];
        NSLog(@"%@", string);

字符串拼接 "---<辉哥语录>"

 [string appendString:@"---<辉哥语录>"];
        NSLog(@"%@", string);

字符串的插入

   NSMutableString *string1 = [[NSMutableString alloc]initWithFormat:@"我与有个约会"];
        [string1 insertString:@"天使" atIndex:2];
        NSLog(@"%@", string1);

字符串的删除

 NSMutableString *string2 = [[NSMutableString alloc] initWithFormat:@"我想找个女汉子"];
        [string2 deleteCharactersInRange: NSMakeRange(4, 1)];
        NSLog(@"%@", string2);

字符串的替换

 NSMutableString *string3 = [[NSMutableString alloc] initWithFormat:@"我想找个月薪1w的工作"];
        [string3  replaceCharactersInRange:NSMakeRange(4, 1) withString:@"日"];
        NSLog(@"%@", string3);