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# Form and Multipart Handling
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Form data and multipart request body construction for file uploads and form submissions.
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## FormBody
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For application/x-www-form-urlencoded requests.
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```kotlin { .api }
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class FormBody private constructor() : RequestBody() {
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    val size: Int
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    fun encodedName(index: Int): String
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    fun name(index: Int): String
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    fun encodedValue(index: Int): String
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    fun value(index: Int): String
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    class Builder {
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        fun add(name: String, value: String): Builder
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        fun addEncoded(name: String, value: String): Builder
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        fun build(): FormBody
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    }
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}
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```
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## MultipartBody
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For multipart/form-data requests, typically used for file uploads.
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```kotlin { .api }
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class MultipartBody private constructor() : RequestBody() {
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    val type: MediaType
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    val boundary: String
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    val size: Int
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    fun part(index: Int): Part
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    fun parts(): List<Part>
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    class Builder {
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        constructor()
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        constructor(boundary: String)
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        fun setType(type: MediaType): Builder
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        fun addPart(body: RequestBody): Builder
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        fun addPart(headers: Headers?, body: RequestBody): Builder
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        fun addFormDataPart(name: String, value: String): Builder
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        fun addFormDataPart(name: String, filename: String?, body: RequestBody): Builder
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        fun build(): MultipartBody
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    }
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    class Part private constructor() {
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        val headers: Headers?
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        val body: RequestBody
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        companion object {
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            fun create(body: RequestBody): Part
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            fun create(headers: Headers?, body: RequestBody): Part
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            fun createFormData(name: String, value: String): Part
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            fun createFormData(name: String, filename: String?, body: RequestBody): Part
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        }
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    }
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    companion object {
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        val MIXED: MediaType
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        val ALTERNATIVE: MediaType
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        val DIGEST: MediaType
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        val PARALLEL: MediaType
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        val FORM: MediaType
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    }
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}
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```
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### File Upload Example
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```kotlin
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val file = File("photo.jpg")
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val requestBody = file.asRequestBody("image/jpeg".toMediaType())
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val multipartBody = MultipartBody.Builder()
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    .setType(MultipartBody.FORM)
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    .addFormDataPart("title", "My Photo")
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    .addFormDataPart("photo", "photo.jpg", requestBody)
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    .build()
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val request = Request.Builder()
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    .url("https://api.example.com/upload")
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    .post(multipartBody)
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    .build()
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```