字符串中带有emoji表情如果不进行特殊处理, 在作为参数发送网络请求时会失败, 但是又避免不了终端用户输入emoji表情, 所以需要在请求网络前进行判断:
我是写在NSString (Extension)分类中, 写一个类方法:

+ (BOOL)stringContainsEmoji:(NSString *)string
{
    __block BOOL returnValue = NO;
    
    [string enumerateSubstringsInRange:NSMakeRange(0, [string length])
                               options:NSStringEnumerationByComposedCharacterSequences
                            usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {
                                const unichar hs = [substring characterAtIndex:0];
                                if (0xd800 <= hs && hs <= 0xdbff) {
                                    if (substring.length > 1) {
                                        const unichar ls = [substring characterAtIndex:1];
                                        const int uc = ((hs - 0xd800) * 0x400) + (ls - 0xdc00) + 0x10000;
                                        if (0x1d000 <= uc && uc <= 0x1f77f) {
                                            returnValue = YES;
                                        }
                                    }
                                } else if (substring.length > 1) {
                                    const unichar ls = [substring characterAtIndex:1];
                                    if (ls == 0x20e3) {
                                        returnValue = YES;
                                    }
                                } else {
                                    if (0x2100 <= hs && hs <= 0x27ff) {
                                        returnValue = YES;
                                    } else if (0x2B05 <= hs && hs <= 0x2b07) {
                                        returnValue = YES;
                                    } else if (0x2934 <= hs && hs <= 0x2935) {
                                        returnValue = YES;
                                    } else if (0x3297 <= hs && hs <= 0x3299) {
                                        returnValue = YES;
                                    } else if (hs == 0xa9 || hs == 0xae || hs == 0x303d || hs == 0x3030 || hs == 0x2b55 || hs == 0x2b1c || hs == 0x2b1b || hs == 0x2b50) {
                                        returnValue = YES;
                                    }
                                }
                            }];
    
    return returnValue;
}

另外在textView的代理方法中也可以直接过滤掉手动输入的emoji表情:
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text {
    if ([[[UITextInputMode currentInputMode] primaryLanguage] isEqualToString:@"emoji"]) {
        return NO;
    }
    return YES;
}