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Kotlin extensions for expressing a single if-else statement and boolean

Kotlin extensions for expressing a single if-else statement and boolean

WhatIf

☔ WhatIf is kotlin extensions for expressing a single if-else statement, nullable and boolean.

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Jitpack

Gradle

Add a dependency code to your module's build.gradle file.

dependencies {
    implementation "com.github.skydoves:whatif:1.0.0"
}

Usage

WhatIf

WhatIf is an expression for invoking whatIf lambda when the given boolean is true and not-null.

val nullableBoolean: Boolean? = true
whatIf(nullableBoolean) {
  log("not-null and true : $nullableBoolean")
}

Here is an extension for nullable booleans.

nullableBoolean.whatIf {
  log("not-null and true : $nullableBoolean")
}

WhatIfNot

The whatIf expression is basically composed with given, whatIf, whatIfNot.

If the target is null or false, whatIfNot will be invoked instead of the whatIf.

If we do not need to handle whatIfNot case, it can be omitted.

whatIf(
  given = nullableBoolean,
  whatIf = { log("not-null and true : $nullableBoolean") },
  whatIfNot = { log("null or false : $nullableBoolean") }
)

Or here is an extension for nullable boolean.

nullableBoolean.whatIf(
  whatIf = { log("not-null and true : $nullableBoolean") },
  whatIfNot = { log("not-null or false : $nullableBoolean") }
)

WhatIf in the builder pattern

Sometimes we should set builder differently to depend on options.

WhatIf is useful when using a chaining function like a builder pattern.

It can be applied to any builder patterns like AlertDialog.Builder or anything.

val balloon = Balloon.Builder(baseContext)
  .setArrowSize(10)
  .setArrowVisible(true)
  .whatIf(nullableBoolean) { setTextColor(Color.YELLOW) }
  .whatIf(nullableBoolean, { setText("Hello, whatIf") }, { setText("Good-Bye whatIf") })
  .setWidthRatio(1.0f)
  .build()

WhatIfNotNull

WhatIfNotNull is an expression for invoking [whatIf] lambda when the target object is not null.

val nullableObject: Person? = Person()
nullableObject.whatIfNotNull {
  log("$it is not null")
}

And we can handle the null case.

If the target is null, [whatIfNot] will be invoked instead of the [whatIf].

nullableObject.whatIfNotNull(
  whatIf = { log("$it is not null.") },
  whatIfNot = { log("$it is null.") }
)

WhatIfLet

The basic concept is the same as whatIf but it is useful when the receiver and the result should be different.

val length = nullableString?.whatIfLet(
  given = nullableString.length < 5,
  whatIf = { it.length },
  whatIfNot = {
    log("$it, length can not over than 5.")
    5
  }
)

We can use default value instead of the whatIfNot and can be omitted the whatIfNot.

val length = nullableString?.whatIfLet(
  nullableString.length < 5,
  default = nullableString.length) { 
  log("$it, length can not over than 5.")
  5
}

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