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    fluid-chains

    0.5.10 • Public • Published

    Fluid-chains

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    A simple way to organize asynchronous Javascript functions that looks like this:

    alt text

    And turn it into something like this: (ES6)

    alt text

    Table of Contents

    Getting Started

    Installing fluid-chains is easy. We want to make it light and simple.

    Installation

    npm install --save fluid-chains
    
    • Javascript (ES6)
    import {Chain} from 'fluid-chains';
    • Javascript
    var FluidChains = require('fluid-chains');
    var Chain  = FluidChains.Chain;

    Creating your first chain

    new Chain('FindPeople', function(context, param, next) {
        var people = ['john','jane','sam'];
        context.set('people', people.filter(
          function(person) { 
             person === param.filterBy() 
            }));
          next();
    });
     

    Starting the chain

    • ES6
    import {ExecuteChain} from 'fluid-chains';
    • Javascript
    var FluidChains = require('fluid-chains');
    var ExecuteChain = FluidChains.ExecuteChain;
    ExecuteChain('FindPeople', {filterBy: 'jane'}, 
        function(result) {
           var people = result.people();;
         console.log('people', people);
    });

    Creating chain sequence

    new Chain('firstChain', function(context, param, next) {
        /* 
            context.set(key, value) will set 
            param value of the next chain. 
        */ 
        if (param.name) {
            context.set('remarksTo', param.name());
        } else {
            context.set('remarksTo','everyone');
        }
     
        next(); 
        /* call to proceed to the next chain. 
        Good for asynchronous callbacks */
     
    }, 'secondChain' /* name of the next chain */); 
     
    new Chain('secondChain', function(context, param, next) { 
     
        /* 
            the context value of the previous chain can
            be accessed with param.{field}() and it's always
            a Function.
        */
        
        context.set('remarks','Hello, '+param.remarksTo()+'!');
     
        next(); 
        /* not calling next() will break the chain 
        and will not trigger the callback below.*/
    });
     
    ExecuteChain('firstChain', function(result) {
        /* 
            This will run because you call next()
            from the last chain.
        */
        console.log(result.remarks());
    });

    Note: You cannot put Function as a value in context.set(key, value). You can put value and object.

    Reusing Chains

    ExecuteChains(Array, Parameter, Done);

    new Chain('first', function(context,param, next){
       // param.host() can be accessed here
       next()},'second');
    new Chain('second', function(context,param,next) {
       next()},'third');
    new Chain('third', function(context,param,next {
       // param.host() can be accessed here
       next()},'fourth');
    new Chain('fourth', function(context,param,next) {
       next()});
     
    ExecuteChain(['first','third'],{host: 'http://localhost'}, function(result) {
        // last chain processed was "third"
    });
     

    Note: Executing chains like the sample above will ignore the chain's predefined sequence and it will follow the chain sequence in the array. The sample above will run the "first" chain then "third" as long as you satify their parameter and it will complete the sequence even if there is a sequence defined in the "third" chain (which is the "fourth") thus make the chains reuseable.

    Additional note: Parameters can be used throughout the chains.

    Error handling

    You can also use a chain as an error handler. Basically you're just creating another chain.

     
    new Chain('firstChain', function(context, param, next) {
     
        /* 
            context.set(key, value) will set param value of the 
            next chain. 
        */ 
     
        if (param.name) {
            context.set('remarksTo', param.name());
        } else {
          throw new Error('Name is required.');
        }
        next();
     
    }, 'secondChain', 'firstErrorHandler' 
      /*error handler is on the fourth argument*/); 
     
    new Chain('firstErrorHandler', function(context, param, next) { 
        /*
            param.$error and param.$errorMessage functions
            are created.
        */
        console.log('error', param.$error());  
            // Error('Name is required.');
        console.log('errorMessage', param.$errorMessage()); 
            // 'Name is required.'
        next(); 
        /* 
            You can call next() to finish the chain or 
            just ignore it and break the chain. 
            You can even start a new chain of actions. 
        */
    });

    Note: You can place an error handler for each chain otherwise it will be thrown to the nearest error handler of its previous chain.

    new Chain('firstChain', function(context, param, next) {
        if (param.name){
            context.set('remarksTo', param.name());
        } else {
            context.set('remarksTo','everyone');
        }
        next();
     
    }, 'secondChain', 'firstErrorHandler'); 
     
    new Chain('secondChain', function(context, param, next) {
        context.set('remarks','Hello, '+param.remarksTo()+'!');
        next();
     
    }, 'thirdChain', 'anotherErrorHandler'); 
     
    new Chain('thirdChain', function(context, param, next) {
       if (param.name){
            context.set('remarksTo', param.name());
        } else {
          throw new Error('Name is required.');
        }
        next();
    }); 
     
    new Chain('firstErrorHandler', function(context, param, next) { 
        console.log('error', param.$error());  
            // Error('Name is required.');
        console.log('errorMessage', param.$errorMessage()); 
            // 'Name is required.'
        next();
    });
     
    new Chain('anotherErrorHandler', function(context, param, next) { 
        //thirdChain error will also be handled here.
        next();
    });

    Note: For asynchronous callback errors you may do "next(Error)".

    new Chain('firstChain', function(context, param, next) {
        setTimeout(function() {
            next(new Error('sample'));
        });
    }, 'secondChain', 'firstErrorHandler'); 

    Using decorator

    You can create a chain by using decorator @ChainAction.

    import {ChainAction, ExecuteChain} from 'fluid-chains';
     
    class Student {
     
        @ChainAction
        createStudent(context, param, next) {
            //param.name();
            //context.set('studentId',####);
        }
     
        @ChainAction
        findAll(context, param, next) {
     
        }
     
    }
     
    const student = new Student();
     
    ExecuteChain(student.CHAIN_CREATESTUDENT, {
            name:'John Doe'
        }, result =>{
            //result.studentId
        })
    // student.CHAIN_FINDALL
    // student.CHAIN_CREATESTUDENT

    ChainAction can only be used in a function inside a class. It will initialize a chain based on the function name and will set a string constant CHAIN_{Name of the function in upper case} in the current class.

    Adding specifications and validation

    For each chain we can specify required fields and custom validations

    var FindPeopleChain = new Chain('FindPeople', function(context, param, next) { 
        param.name() // should not be null or empty
        param.type() // should not be null or empty and must be "quick"
        next();
    });
     
    /*
        @param field: string,
        @param required: boolean
        @param customerValidation (Optional) : Function(callback) => callback(valid, message)
    */
    FindPeopleChain.addSpec('name', true);
    FindPeopleChain.addSpec('type',true, function(done) {
        done(type ==='quick', 'Type should be "quick"'); });
     
    // or
     
    FindPeopleChain.addSpec('email').require('custom message').validator((currentValue, valid)=>{
        valid(currentValue.match('email regex here'));
    });
     

    Strict mode

    You can turn on strict mode by invoking "ChainStrictModeEnabled" function.

    • ES6
    import {ChainStrictModeEnabled} from 'fluid-chains';
    ChainStrictModeEnabled();
    • Javascript
    var FluidChains = require('fluid-chains');
    var ChainStrictModeEnabled = FluidChains.ChainStrictModeEnabled;
    ChainStrictModeEnabled();

    With strict mode "on", chains can will only accept parameter that is specified in addSpec.

     new Chain('StrictModeChain01', function(context, param, next) {
        context.set('name', 'John');
        context.set('surname', 'Wick');
        context.set('age', 'unknown');
        next();
     }, 'StrictModeChain02');
     
     
    var strictChain = new Chain('StrictModeChain02', function(context, param, next) {
        param.name() // is available
        param.surname() // is available
        param.age() // is not available 
        next();
    }, null, null);
     
    strictChain.addSpec('name', true);
    strictChain.addSpec('surname', true)
     

    Caching

    Since the chain output can be based on the value of its parameter making it possible to cache the output of a chain.

    To enable caching you must have strict mode enabled.

    • ES6
    import {ChainStrictModeEnabled, ChainCacheEnabled} from 'fluid-chains';
    ChainStrictModeEnabled();
    ChainCacheEnabled();
    • Javascript
    var FluidChains = require('fluid-chains');
    var ChainStrictModeEnabled = FluidChains.ChainStrictModeEnabled;
    var ChainCacheEnabled = FluidChains.ChainCacheEnabled;
    ChainStrictModeEnabled();
    ChainCacheEnabled();

    Note: Only the fields specified in Chain.addSpec() will be used as identifier of the chain cache. If Chain.addSpec() are not used it will cache the chain using its name.

    Running with Middlewares

    • ES6
    import { ChainMiddleware } from 'fluid-chains';
    • Javascript
    var FluidChains = require('fluid-chains');
    var ChainMiddleware = FluidChains.ChainMiddleware;
    /*
    * Will only get here before chain 'FindPeople' is executed
    */
    new ChainMiddleware('FindPeople', function(param, context, next) { 
        next();
    });
     
    /*
    * Will only get here before chain name that starts with "Find" is executed
    */
    new ChainMiddleware(\^Find\g, function(param, context, next) { 
        if(context.$next() === 'CreatePeopleChain' && param.sessionKey){
            //validates 
        } else {
            throw new Error('Chain authentication failed.');
        }
        next();
    });
     
    /*
    * Will run before every chains
    */
    new ChainMiddleware(function(param, context, next) {
       console.log('param',param.$owner());
       next();
    });
     

    How it works

    alt text

    alt text

    Examples

    Documentation

    Chain

    The star of this package.

     
        var chainSample = new Chain('ChainSample', function(context, param) {
            // do something
        })

    constructor(name:String, action:Function, next:String, errorHandler:String)

    • name: defines the name of the chain
    • action: function(context:ChainContext, param: ChainContext, [next:Function])
      • context: context of the current chain
      • param: consist of root parameters and context or the previous chain
      • next (optional): triggers the callback of the chain
    • next: defines the next chain in sequence
    • errorHandler: defines the name of the error handler chain

    Note: chain will run synchronously if next is not defined in action parameters

    field description usage
    addSpec() sets the chain parameter spec chain.addSpec(ChainSpec)
    info() returns the name, status & response time chain.info()
    status() returns thes current status of chain chain.status()
    terminate() stops the running chain chain.terminate()
    execute() executes the chain chain.execute(callback, ChainContext, NextChain, disableNext)

    ChainSpec

    Defines the input of the chain.

       var chainSample = new Chain('ChainSample', function(context, param) {
        param.name() // this is required for this chain
        param.email() // this is required for this email and validated before going here
       });
       
       chainSample.addSpec('name', true);
       chainSample.addSpec('user')
                .transform(function(currentValue, newForm){
                    if(currentValue){
                        findUser(currentValue, function(userData) {
                            newForm(userData);
                        });
                    }
                });
       chainSample.addSpec('email')
                .require()
                .validator(function(currentValue, valid) {
                    valid(currentValue.match(/email-regex/g));
                });
       chainSample.addSpec('fullname')
                .translate(function(currentValue, context) {
                    const names = currentValue.split(',');
                    context.set('lastname', names[0]);
                    context.set('firstname', names[1]);
                });       
       
    field description usage
    require() mark the field as a required input in chain chain.addSpec(field:String).require(customMessage:String)
    default() defines the default value chain.addSpec(field:String).default(value:String)
    validator() defines the validator chain.addSpec(field:String).validator(validate:Function)
    transform() defines the transformer chain.addSpec(field:String).transform(transformer:Function)
    translate() defines the translator chain.addSpec(field:String).translate(translator:Function)

    ChainMiddleware

    constructor(target:String, action:Function(param:ChainContext, context:ChainContext, next:Function(err:Error)));

    new ChainMiddleware('{targetChainName}', function(param, context, next) {
        next();
       });
     
    • target: defines the name of the target chain
    • action: function(param:ChainContext, context: ChainContext, [next:Function])
      • param: consist of root parameters and context of the previous chain
      • context: context of the target chain
      • next (optional): triggers the callback of the chain

    ExecuteChain

    Executes and composes sequence of chains.

    • function([name:String|Array], parameters, callback);
        
        ExecuteChain('ChainSample', {
            hello: 'hello'
         }, function(result) {
         
         });
         
          ExecuteChain(['ChainSample','ChainSample_2'], {
            hello: 'hello'
         }, function(result) {
         
         });
         

    ChainExists

    Availability checker of chain in the current instance.

    ChainExists = function(name:String):Boolean

    ChainList

    Returns an array of all the available chains in the current instance

    Authors

    See also the list of contributors who participated in this project.

    License

    This project is licensed under the MIT License - see the LICENSE.md file for details

    Install

    npm i fluid-chains

    DownloadsWeekly Downloads

    12

    Version

    0.5.10

    License

    ISC

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