Change text input color for hashtags react native mobx

I want to dynamically change the color of words in a textInput element where a hashtag comes up. Similar to a lot of apps. Here is what i have so far:

@observable descriptionString: any = '';@observable formattedText: any = ;handleCheckTextChange = (inputText:any) => {    const words = inputText.split('');    console.log(words);    const formattedText:any = [];    words.forEach((word:any, index:any) => {      const isLastWord = index === words.length - 1;      if (!word.startsWith('@')) {        return isLastWord ? formattedText.push(word) : formattedText.push(word, '');      }      const mention = (<Text key={word + index} style={{color: 'red'}}>          {word}</Text>      );      isLastWord ? formattedText.push(mention) : formattedText.push(mention, '');    });    this.formattedText = formattedText;  }

The text input:

<TextInput            maxLength={descriptionMaxLength}            multiline={true}            placeholder='Type description here'            style={styles.descriptionInput}            returnKeyType='next'            blurOnSubmit={true}            onChangeText={(text) => this.handleCheckTextChange(text)}><Text>{this.formattedText}</Text></TextInput>

I got this from another stack overflow question, but it doesn't seem to work with my code. Getting a mobx error saying "Dynamic observable objects cannot be frozen." I am using mobx for state handling and the error is a mobx error so i am think that this may be an issue with setting and changing that formattedText observable. Any help is appreciated!