When the same code is duplicated in two or more separate branches of a conditional, it can make the code harder to understand, maintain, and can
potentially introduce bugs if one instance of the code is changed but others are not.
Having two cases in a switch statement or two branches in an if chain with the same implementation is at
best duplicate code, and at worst a coding error.
if a >= 0 && a < 10 {
doFirstThing()
doSomething()
} else if a >= 10 && a < 20 {
doSomethingElse()
} else if a >= 20 && a < 50 { // Noncompliant; duplicates first condition
doFirstThing()
doSomething()
} else {
doTheRest()
}
switch i {
case 1:
doFirstThing()
doSomething()
case 2:
doSomethingElse()
case 3: // Noncompliant; duplicates case 1's implementation
doFirstThing()
doSomething()
default:
doTheRest()
}
If the same logic is truly needed for both instances, then:
- in an
if chain they should be combined
if (a >= 0 && a < 10) || (a >= 20 && a < 50) {
doFirstThing()
doSomething()
} else if a >= 10 && a < 20 {
doSomethingElse()
} else {
doTheRest()
}
- for a
switch, the values should be put in the case expression list.
switch i {
case 1, 3:
doFirstThing()
doSomething()
case 2:
doSomethingElse()
default:
doTheRest()
}
Exceptions
Blocks in an if chain or case blocks that contain a single line of code are ignored.
if a == 1 {
doSomething() //no issue, usually this is done on purpose to increase the readability
} else if a == 2 {
doSomethingElse()
} else {
doSomething()
}
