- Qt 6.12
- Qt Qml
- QML Lint Warning and Errors
- Loose equality comparison type coercion
- Qt 6.12.0 Reference Documentation

# Loose equality comparison type coercion

This warning category is spelled `[equality-type-coercion]` by qmllint.

## Loose equality comparison type coercion

### What happened?

Two values were compared for equality using the loose comparison operators.

### Why is that bad?

The loose comparison operators can coerce values to a different type before checking for equality. This can lead to unexpected results.

### Example

Here is an example with a list of Rectangles and a TextInput. When the user enters a number, the Rectangle at that index is highlighted. The code has a flaw. If the input is empty, the first rectangle is highlighted in red, because "" == 0.

     import QtQuick

     Item {
         TextInput {
             id: input
         }
         Repeater {
             model: 3
             Rectangle {
                 // first rectangle is red on empty input
                 color: input.text == index ? "red" : "blue"
             }
         }
     }

In general, use the strict comparison operators `===` and `!==`. Even if you are aware of the coercion, it is still recommended to use explicit casts and strict comparisons instead.

     import QtQuick

     Item {
         TextInput {
             id: input
         }
         Repeater {
             model: 3
             Rectangle {
                 // check inputs, use explicit casts, and strict equality operators
                 color: input.text.length !== 0
                        && Number(input.text) === index ? "red" : "blue"
             }
         }
     }