CODEWITHSUNDEEP
groovydynamiccontains
caeus
caeus

Reputation: 3696

Groovy: Why the "in" operator when used in maps of booleans has such a weird behaviour?

Basically this happens

def map =   [a:"Hello", b: "World", c: true, d: false]

println("a" in map) // true
println("b" in map) // true
println("c" in map) // true
println("d" in map) // false WHY????

Upvotes: 2

Views: 179

Answers (1)

user16358266
user16358266

Reputation: 407

The in operator, or rather the Membership Operator is represented by the isCase method, which was originally added for switch statements.

I can't tell you why they decided to implement it this way, but it is implemented like this for Maps:

org.codehaus.groovy.runtime.DefaultGroovyMethods#isCase(java.util.Map, java.lang.Object)


    /**
     * 'Case' implementation for maps which tests the groovy truth
     * value obtained using the 'switch' operand as key.
     * For example:
     * <pre class="groovyTestCase">switch( 'foo' ) {
     *   case [foo:true, bar:false]:
     *     assert true
     *     break
     *   default:
     *     assert false
     * }</pre>
     *
     * @param caseValue   the case value
     * @param switchValue the switch value
     * @return the groovy truth value from caseValue corresponding to the switchValue key
     * @since 1.7.6
     */
    public static boolean isCase(Map caseValue, Object switchValue) {
        return DefaultTypeTransformation.castToBoolean(caseValue.get(switchValue));
    }

If you want to be certain to check only the keys you need to write something like this x in map.keys().

Upvotes: 3

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