Functions with a long parameter list are difficult to use because maintainers must figure out the role of each parameter and keep track of their
position.
function setCoordinates(x1, y1, z1, x2, y2, z2) { // Noncompliant
// ...
}
The solution can be to:
- Split the function into smaller ones
// Each function does a part of what the original setCoordinates function was doing, so confusion risks are lower
function setOrigin(x, y, z) {
// ...
}
function setSize(width, height, depth) {
// ...
}
- Find a better data structure for the parameters that group data in a way that makes sense for the specific application domain
// In geometry, Point is a logical structure to group data
let point1 = { x: x1, y: y1, z: z1};
let point2 = { x: x1, y: y1, z: z1};
setCoordinates(point1, point2);
function setCoordinates(p1, p2) {
// ...
}
This rule raises an issue when a function has more parameters than the provided threshold.
Exceptions
The rule ignores TypeScript parameter properties when counting parameters:
class C {
constructor(
private param1: number, // ignored
param2: boolean, // counted
public param3: string, // ignored
readonly param4: string[], // ignored
param5: number | string // counted
) {} // Compliant by exception
}
The rule also ignores Angular component constructors:
import { Component } from '@angular/core';
@Component({/* ... */})
class Component {
constructor(p1, p2, p3, p4, p5) {} // Compliant by exception
}
