Question

我是java程序员，“必须”继续使用obj-C一段时间，

在生成随机字母数字代码时我有些困惑...这里是我的javacode：

PS：我想生成如下代码：Gh12PU67，AC88pP13，Bk81gH89

private String generateCode(){
 String code = "";
 Random r = new Random();
 char[] c = new char[]{'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};

 for(int i = 0; i<4; i++){
  int uplow = r.nextInt(2);
  String temp = ""+ c[r.nextInt(c.length)];
  if(uplow==1)
   code = code + temp.toUpperCase();
 else
   code = code + temp;

 if((i+1)%2==0){
   code += r.nextInt(10);
   code += r.nextInt(10);
 }
}

return code;
}

然后我在OBJ-C上创建

-(void)generateCode{
    NSString *alphabet  = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXZY0123456789";
    NSMutableString *s = [NSMutableString stringWithCapacity:4];
    for (NSUInteger i = 0U; i < 4; i++) {
        u_int32_t r = arc4random() % [alphabet length];
        unichar c = [alphabet characterAtIndex:r];
        [s appendFormat:@"%C", c];

    }
    NSLog(@"s-->%@",s);
}

但我得到“HpNz”的结果AC88pP13 insted hve pattern String，string，numeric，numeric，lowescase string，numeric，numeric ...

那个案子让我的生活停了3天......

Answer 1

你的Objective-C代码看起来不错，但是（正如@Wain在上面的评论中正确地说的那样）， Java函数函数包含在2个字母后面插入2位数字的逻辑没有在Objective-C方法中复制。

我会把这个逻辑略微模糊不清，并把它写成

- (void)generateCode
{
    static NSString *letters = @"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXZY";
    static NSString *digits = @"0123456789";
    NSMutableString *s = [NSMutableString stringWithCapacity:8];
    for (NSUInteger i = 0; i < 2; i++) {
        uint32_t r;

        // Append 2 random letters:
        r = arc4random_uniform((uint32_t)[letters length]);
        [s appendFormat:@"%C", [letters characterAtIndex:r]];
        r = arc4random_uniform((uint32_t)[letters length]);
        [s appendFormat:@"%C", [letters characterAtIndex:r]];

        // Append 2 random digits:
        r = arc4random_uniform((uint32_t)[digits length]);
        [s appendFormat:@"%C", [digits characterAtIndex:r]];
        r = arc4random_uniform((uint32_t)[digits length]);
        [s appendFormat:@"%C", [digits characterAtIndex:r]];

    }
    NSLog(@"s-->%@",s);
}

备注（来自手册页）： arc4random_uniform(length)优先于arc4random() % length，因为当上限不是2的幂时，它避免了“模偏差”。

备注： Java代码code += r.nextInt(10);的逐字翻译到Objective-C将是

r = arc4random_uniform(10);
[s appendString:[@(r) stringValue]];

从随机数创建NSNumber对象@(r)，然后将其转换为字符串。

Answer 2

如果你想要一个安全的随机字符串，你应该使用这个代码：

#define ASCII_START_NUMERS 0x30
#define ASCII_END_NUMERS 0x39

#define ASCII_START_LETTERS_A 0x41
#define ASCII_END_LETTERS_Z 0x5A

#define ASCII_START_LETTERS_a 0x61
#define ASCII_END_LETTERS_z 0x5A

-(NSString *)getRandomString:(int)length {
    NSMutableString *result = [[NSMutableString alloc]init];
    while (result.length != length) {
        NSMutableData* data = [NSMutableData dataWithLength:1];
        SecRandomCopyBytes(kSecRandomDefault, 1, [data mutableBytes]);
        Byte currentChar = 0;
        [data getBytes:&currentChar length:1];
        NSString *s = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        if (currentChar > ASCII_START_NUMERS && currentChar < ASCII_END_NUMERS) { // 0 to 0
            [result appendString:s];
            continue;
        }
        if (currentChar > ASCII_START_LETTERS_A && currentChar < ASCII_END_LETTERS_Z) { // A to Z
            [result appendString:s];
            continue;
        }
        if (currentChar > ASCII_START_LETTERS_a && currentChar < ASCII_END_LETTERS_z) { // a to z
            [result appendString:s];
            continue;
        }
    }
    return result;
}

在IOS上创建随机字母数字

2 个答案: