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Principal

Module for interacting with Principals (users and canisters).

Principals are used to identify entities that can interact with the Internet Computer. These entities are either users or canisters.

Example textual representation of Principals:

un4fu-tqaaa-aaaab-qadjq-cai

In Motoko, there is a primitive Principal type called Principal. As an example of where you might see Principals, you can access the Principal of the caller of your shared function.

shared(msg) func foo() {
  let caller : Principal = msg.caller;
};

Then, you can use this module to work with the Principal.

Import from the base library to use this module.

import Principal "mo:base/Principal";

Type Principal​

type Principal = Prim.Types.Principal

Function fromActor​

func fromActor(a : actor {  }) : Principal

Get the Principal identifier of an actor.

Example:

actor MyCanister {
  func getPrincipal() : Principal {
    let principal = Principal.fromActor(MyCanister);
  }
}

Function toBlob​

func toBlob(p : Principal) : Blob

Convert a Principal to its Blob (bytes) representation.

Example:

let principal = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
let blob = Principal.toBlob(principal); // => \00\00\00\00\00\30\00\D3\01\01

Function fromBlob​

func fromBlob(b : Blob) : Principal

Converts a Blob (bytes) representation of a Principal to a Principal value.

Example:

let blob = "\00\00\00\00\00\30\00\D3\01\01" : Blob;
let principal = Principal.fromBlob(blob);
Principal.toText(principal) // => "un4fu-tqaaa-aaaab-qadjq-cai"

Function toText​

func toText(p : Principal) : Text

Converts a Principal to its Text representation.

Example:

let principal = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
Principal.toText(principal) // => "un4fu-tqaaa-aaaab-qadjq-cai"

Function fromText​

func fromText(t : Text) : Principal

Converts a Text representation of a Principal to a Principal value.

Example:

let principal = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
Principal.toText(principal) // => "un4fu-tqaaa-aaaab-qadjq-cai"

Function isAnonymous​

func isAnonymous(p : Principal) : Bool

Checks if the given principal represents an anonymous user.

Example:

let principal = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
Principal.isAnonymous(principal) // => false

Function hash​

func hash(principal : Principal) : Hash.Hash

Hashes the given principal by hashing its Blob representation.

Example:

let principal = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
Principal.hash(principal) // => 2_742_573_646

Function compare​

func compare(principal1 : Principal, principal2 : Principal) : {#less; #equal; #greater}

General purpose comparison function for Principal. Returns the Order ( either #less, #equal, or #greater) of comparing principal1 with principal2.

Example:

let principal1 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
let principal2 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
Principal.compare(principal1, principal2) // => #equal

Function equal​

func equal(principal1 : Principal, principal2 : Principal) : Bool

Equality function for Principal types. This is equivalent to principal1 == principal2.

Example:

let principal1 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
let principal2 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
ignore Principal.equal(principal1, principal2);
principal1 == principal2 // => true

Note: The reason why this function is defined in this library (in addition to the existing == operator) is so that you can use it as a function value to pass to a higher order function. It is not possible to use == as a function value at the moment.

Example:

import Buffer "mo:base/Buffer";

let buffer1 = Buffer.Buffer<Principal>(3);
let buffer2 = Buffer.Buffer<Principal>(3);
Buffer.equal(buffer1, buffer2, Principal.equal) // => true

Function notEqual​

func notEqual(principal1 : Principal, principal2 : Principal) : Bool

Inequality function for Principal types. This is equivalent to principal1 != principal2.

Example:

let principal1 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
let principal2 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
ignore Principal.notEqual(principal1, principal2);
principal1 != principal2 // => false

Note: The reason why this function is defined in this library (in addition to the existing != operator) is so that you can use it as a function value to pass to a higher order function. It is not possible to use != as a function value at the moment.

Function less​

func less(principal1 : Principal, principal2 : Principal) : Bool

"Less than" function for Principal types. This is equivalent to principal1 < principal2.

Example:

let principal1 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
let principal2 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
ignore Principal.less(principal1, principal2);
principal1 < principal2 // => false

Note: The reason why this function is defined in this library (in addition to the existing < operator) is so that you can use it as a function value to pass to a higher order function. It is not possible to use < as a function value at the moment.

Function lessOrEqual​

func lessOrEqual(principal1 : Principal, principal2 : Principal) : Bool

"Less than or equal to" function for Principal types. This is equivalent to principal1 <= principal2.

Example:

let principal1 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
let principal2 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
ignore Principal.lessOrEqual(principal1, principal2);
principal1 <= principal2 // => true

Note: The reason why this function is defined in this library (in addition to the existing <= operator) is so that you can use it as a function value to pass to a higher order function. It is not possible to use <= as a function value at the moment.

Function greater​

func greater(principal1 : Principal, principal2 : Principal) : Bool

"Greater than" function for Principal types. This is equivalent to principal1 > principal2.

Example:

let principal1 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
let principal2 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
ignore Principal.greater(principal1, principal2);
principal1 > principal2 // => false

Note: The reason why this function is defined in this library (in addition to the existing > operator) is so that you can use it as a function value to pass to a higher order function. It is not possible to use > as a function value at the moment.

Function greaterOrEqual​

func greaterOrEqual(principal1 : Principal, principal2 : Principal) : Bool

"Greater than or equal to" function for Principal types. This is equivalent to principal1 >= principal2.

Example:

let principal1 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
let principal2 = Principal.fromText("un4fu-tqaaa-aaaab-qadjq-cai");
ignore Principal.greaterOrEqual(principal1, principal2);
principal1 >= principal2 // => true

Note: The reason why this function is defined in this library (in addition to the existing >= operator) is so that you can use it as a function value to pass to a higher order function. It is not possible to use >= as a function value at the moment.