Question

我正在尝试为String转换编写一个通用方法（目的是为RESTful API编写解析器）。

该消息旨在按如下方式转换字符串

creationTSZ - ＆gt; creation_tsz

userId - ＆gt; USER_ID

邮件处理转换userId - ＆gt; user_id，目前无效地循环遍历字符串并更改部分。

尚未处理creationTSZ - ＆gt; creation_tsz，我认为进一步循环是非常低效的，我想知道是否有更好的方法来做到这一点？

可能是正则表达式吗？

-(NSString *)fieldsQueryString 
{

    NSArray *fieldNames = [self fieldList];

    /* Final composed string sent to Etsy */
    NSMutableString *fieldString = [[[NSMutableString alloc] init] autorelease];

    /* Characters that we replace with _lowerCase */
    NSArray *replaceableChars = [NSArray arrayWithObjects:
                                 @"Q", @"W", @"E", @"R", @"T", @"Y", @"U", @"I", @"O", @"P", 
                                 @"A", @"S", @"D", @"F", @"G", @"H", @"J", @"K", @"L",
                                 @"Z", @"X", @"C", @"V", @"B", @"N", @"M", nil];

    /* Reusable pointer for string replacements */
    NSMutableString *fieldNameString = nil;

    /* Loop through the array returned by the filter and change the names */
    for(NSString *fieldName in fieldNames) {
        /* Loop if the field is to be omited */
        if ([[self valueForKey:fieldName] boolValue] == NO) continue;
        /* Otherwise change the name to a field and add it */
        fieldNameString = [fieldName mutableCopy];
        for(NSString *replaceableChar in replaceableChars) {
            [fieldNameString replaceOccurrencesOfString:replaceableChar 
                                             withString:[NSString stringWithFormat:@"_%@", [replaceableChar lowercaseString]] 
                                                options:0 
                                                  range:NSMakeRange(0, [fieldNameString length])];
        }
        [fieldString appendFormat:@"%@,", fieldNameString];
        [fieldNameString release];
    }
    fieldNames = nil;

    /* Return the string without the last comma */
    return [fieldString substringToIndex:[fieldString length] - 1];
}

Answer 1

假设您的标识符的结构类似于

<lowercase-prefix><Uppercase-char-and-remainder>

你可以使用：

NSScaner *scanner = [NSScanner scannerWithString:fieldName];
NSString *prefix = nil;
[scanner scanCharactersFromSet:[NSCharacterSet lowercaseLetterCharacterSet] intoString:&prefix];
NSString *suffix = nil;
[scanner scanCharactersFromSet:[NSCharacterSet letterCharacterSet] intoString:&suffix];
NSString *fieldNameString = [NSString stringWithFormat:@"%@_%@", prefix, [suffix lowercaseString]];

这将执行字段标识符的转换（但是如果前缀或后缀保持为零，则应执行一些错误检查。）

构建fieldNames列表的最简单方法是将它们添加到NSMutableArray中，然后加入它们：

NSMutableArray *fields = [[NSMutableArray alloc] init];
for (NSString *fieldName in [self fieldList]) {
    // code as above
    [fields add:fieldNameString];
}
NSString *commaFields = [fields componentsJoinedByString:@","];
[fields release];
return commaFields;

复杂的Objective-C字符串替换

1 个答案: