map an array of struct

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marshal struct to map
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go map

I have an array of struct containing several fields. I want to map the array to create another one of struct containing a subset of fields

struct History: {
   let field1: String
   let field2: String
   let field3: String
   let field4: String
}

struct SubHistory: {
   let field1: String
   let field2: String
}

I could use the for in loop. But It may be possible to use a map, no ?

Yes, you can use map in the following way:

let histories: [History] // array of History structs
let subHistories = histories.map { SubHistory(field1: $0.field1, field2: $0.field2) }

Store a mapping of addresses linked to arrays of structs, Here is an example : pragma solidity ^0.4.2; contract test { struct my_struct { int a; } mapping (address=>my_struct[]) Map; function fill_map(my_struct struct1� Today, we got introduced to struct, map, array and slice. GO does not have too many data types or collections to be used and hence what we have learned today is what gets used in GO applications. In next post we will learn about functions and pointers.

As a slight variation of kiwisip's correct answer: I would suggest to put the logic of "creating a SubHistory from a History" into a custom initializer:

extension SubHistory {
    init(history: History) {
        self.init(field1: history.field1, field2: history.field2)
    }
}

Then the mapping can be simply done as

let histories: [History] = ...
let subHistories = histories.map(SubHistory.init)

Putting the initializer into an extension has the advantage that the default memberwise initializer is still synthesized – attribution for this observation goes to @kiwisip!

Struct, Map, Array and Slice – letslearngo, Struct GO is not a traditional OO language and hence does not have concept of class. Instead structures are used for holding values. If you are� Therefore you're going to have either use member-access syntax to set the value of the non-static data members, initialize the structs using a list of initialization lists when you declare the array itself, or you can create a constructor for your struct and use the default operator= member function to initialize the array members.

Yes, whenever you have an Array , or any type implementing the Collection protocol, where map is defined, you can use map to transform [A] into [B].

kiwisip already gave a good answer, and Martin R suggested a nice variation.

Here's another one.

extension History {

  var subHistory: SubHistory { 
    return SubHistory(field1: field1, field2: field2)
  }
}

// use it like
let histories: [History] = [...]
let subHistories = histories.map { $0.subHistory }

STRUCT Complex Type (Impala 2.3 or higher only), In the case of a STRUCT directly inside an ARRAY or MAP , you can omit the . ITEM and .VALUE pseudocolumns and refer directly to array_name . field or� Generally Hive supports 4 types of complex data types ARRAY MAP STRUCT UNIONTYPE hive array data type example Hive Array behavior is same as Java Array.It is an ordered collection of elements.The all elements in the array is must be same data type.

A New Functional Approach to Complex Types in Apache Hive , Despite Hive being a very relationally organized system, it has thorough support for complex data types such as Maps, Arrays, and Structs. Using StructType and ArrayType classes we can create a DataFrame with Array of Struct column ( ArrayType(StructType) ). From below example column “booksInterested” is an array of StructType which holds “name”, “author” and the number of “pages”.

Access Data in Structure Array - MATLAB & Simulink, The variables from the file ( X , caption , and map ) are now fields in the structure. Access the data using dot notation of the form structName.fieldName . For� Struct: Struct is a record type which encapsulates a set of named fields that can be any primitive data type. An element in STRUCT type can be accessed using the DOT (.) notation. In our Struct example, we will be using the dataset Bikes.txt where the fields are delimited by tab and the complex type Array values are delimited by the comma.

Map to Different Value Types - MATLAB & Simulink, It is fairly common to store other classes, such as structures or cell arrays, in a Map structure. However, Maps are� Any change in struct will reflect in byte[] array change and vice versa. ++TESTED++ WORKS //FOR DEBUG/TEST ONLY using System.Runtime.InteropServices; namespace

Comments
  • can you add an example of the array you trying to map with an expected result ?
  • let subHistoryArray = historyArray.map{SubHistory(field1: $0.field1, field2: $0.field2)}
  • And if you create the init(history: History) in an extension to SubHistory, you don't have to implement the default initializer as Swift will generate it for you.