WhatIf

Additional

Language
Kotlin
Version
1.0.4 (Sep 17, 2019)
Created
Sep 8, 2019
Updated
Oct 19, 2019
Owner
Jaewoong Eum (skydoves)
Contributor
Jaewoong Eum (skydoves)
1
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Announcement

WhatIf

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

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Gradle

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

dependencies {
    implementation "com.github.skydoves:whatif:1.0.4"
}

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, If we do not need to handle whatIfNot case, it can be omitted.whatIfNot will be invoked instead of the whatIf.


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. It can be applied to any builder patterns like AlertDialog.Builder or anything.WhatIf is useful when using a chaining function like a builder pattern.


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.") }
)

WhatIfNotNullOrEmpty

An expression for invoking whatIf lambda when the string, collections and array type is not null and not empty. If the collections or array type target is null or empty, whatIfNot will be invoked instead of the whatIf.

val nullableString: String? = "NotNullOrEmpty"
nullableString.whatIfNotNullOrEmpty { 
  log("$it is not null and not empty")
}

Here is an example for collections.

nullableList.whatIfNotNullOrEmpty {
  log("list $it is not null and not empty")
}

And we can handle the null or empty case.

nullableList.whatIfNotNullOrEmpty(
  whatIf = { log("list $it is not null and not empty") },
  whatIfNot = { log("list is null or empty") }
)

Here is the same example for the array.

nullableArray.whatIfNotNullOrEmpty {
  log("$it is not null and not empty")
}

Array

Array, ByteArray, ShortArray, IntArray, LongArray, FloatArray, DoubleArray, BooleanArray, CharArray

Collections

List, Map, Set

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
}

WhatIfHasExtras

An expression for invoking whatIf lambda when the Activity's intent extras is not null and not empty.

var foo: String? = null
this@MainActivity.whatIfHasExtras {
  foo = "${it.getString("foo")}"
}

And we can handle the null case.

this@MainActivity.whatIfHasExtras(
   whatIf = { foo = "${it.getString("foo")}" },
   whatIfNot = { log("intent extras is null or empty.") }
)

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License

Copyright 2019 skydoves (Jaewoong Eum)

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.