Efficient Regex Pattern for Getting Hashtags

After digging around the Internet for a while and not finding a regex pattern that was able to produce all of the hashtags in a String, I finally created my own based on information I gathered from a few other places.

\B#[a-zA-Z][a-zA-Z0-9]+

My sources include the following:

• "Best HashTag Regex"
• "RegEx : Perfect hash tag regex"
• "Using Regular Expressions To Match Twitter Users And Hashtags"

I took this information and created a method in Salesforce to grab all of the hashtags from a String and return it in a Set, as shown below.

/**
 * Get the Set of hashtags (including
 * the '#' character) used within a String in
 * all lower case, for ease of comparison.
 *
 * @param  text The String text to analyze.
 * @return      The Set of hashtags
 *              used within the text.
 */
public static Set getHashtagSet(
        String text) {
    
    // Instantiate the resulting set.
    
    Set hashtagSet = new Set();
    
    // Only look for hashtags if text is given.
    
    if (text != null) {
        Pattern hashtagPattern = Pattern.compile(
                '\\B#[a-zA-Z][a-zA-Z0-9]+');
        Matcher hashtagMatcher =
                hashtagPattern.matcher(text);
        
        while (hashtagMatcher.find()) {
            hashtagSet.add(
                hashtagMatcher.group().toLowerCase());
        }   // while (hashtagMatcher.find())
    }   // if (text != null)
    
    // Return the results.
    
    System.debug('hashtagSet = ' + hashtagSet);
    
    return hashtagSet;
}   // public Set getHashtagSet(String)

ISBLANK(String) Returning false When String.length() Returns 0

I discovered this with version 21.0 of the Salesforce API: When a String's length is 0, the ISBLANK(String) Visualforce function will actually return false instead of true.

Visualforce Developer's Guide, Version 21.0 describes the ISBLANK function as follows:

Determines if an expression has a value and returns TRUE if it does not. If it contains a value, this function returns FALSE.

A search for ISNULL in the documentation returned no real results, which makes me wonder if ISNULL has been unofficially deprecated in favor of ISBLANK.

So, it appears that the only way to know for sure whether a String input has been blanked out is to use the length method and compare it to 0.

Conversion Error setting value 'value1 value2 value3' for '#{myMultiselectPicklistValue}'.

Salesforce is great. Apex is great. Visualforce is great.

Until you run into bizarre errors with no obvious explanation, such as the following error:

Conversion Error setting value 'value1 value2 value3' for '#{myMultiselectPicklistValue}'.

This error comes from trying to save the selections from an apex:selectCheckboxes component into a multi-select picklist field. You would think that it's as easy as simply specifying {!property} for the value attribute of the apex:selectCheckboxes component. But, no, it's not.

Multi-select picklist values are stored as String values, with each option delimited with a semicolon.  This is great to know, but what happens with apex:selectCheckboxes? apex:selectCheckboxes expects a List<String>! This discussion board post hints at the annoyance awaiting developers: "Checkboxes not saving".

Basically, to spell it out for myself and for others, here's what we have to do as developers working around this problem.

What we want to write is:


<apex:selectcheckboxes value="{!mPicklistValue}">

... and in the controller ...


public String mPicklistValue { get; set; }

Instead, what we have to write is:


<apex:selectcheckboxes value="{!mPicklistValues}">

... and in the overblown controller ...

private String mPicklistValue;
public List<String> getMPicklistValues() {
    List<String> values = null;
    // Convert mPicklistValue into List of 
    // String values

    if (mPicklistValue != null)
        values = mPicklistValue.split(';');

    return values;
}   // List<String> getMPicklistValues()
public void setMPicklistValues(
        List<String> values) {

    // Convert values into a semilcolon-delimited
    // String value

    if (values == null) {
        mPicklistValue = null;
    }
    else {
        mPicklistValue = '';
        
        for (String value : values) {
            mPicklistValue += value + ';';
        }
    }
}   // void setMPicklistValues(List<String>)

Note the plural name of the custom getter and setter methods. Cheers, indeed.

String Keys for Apex Maps Are Case-sensitive

I discovered today that String keys for Apex Maps are case-sensitive. Apparently the Strings "johndoe" and "JohnDoe" are not equal when being compared to see if the Map contains a key.