28 Matching Annotations
  1. Jan 2024
    1. Instance methods Instances of Models are documents. Documents have many of their own built-in instance methods. We may also define our own custom document instance methods. // define a schema const animalSchema = new Schema({ name: String, type: String }, { // Assign a function to the "methods" object of our animalSchema through schema options. // By following this approach, there is no need to create a separate TS type to define the type of the instance functions. methods: { findSimilarTypes(cb) { return mongoose.model('Animal').find({ type: this.type }, cb); } } }); // Or, assign a function to the "methods" object of our animalSchema animalSchema.methods.findSimilarTypes = function(cb) { return mongoose.model('Animal').find({ type: this.type }, cb); }; Now all of our animal instances have a findSimilarTypes method available to them. const Animal = mongoose.model('Animal', animalSchema); const dog = new Animal({ type: 'dog' }); dog.findSimilarTypes((err, dogs) => { console.log(dogs); // woof }); Overwriting a default mongoose document method may lead to unpredictable results. See this for more details. The example above uses the Schema.methods object directly to save an instance method. You can also use the Schema.method() helper as described here. Do not declare methods using ES6 arrow functions (=>). Arrow functions explicitly prevent binding this, so your method will not have access to the document and the above examples will not work.

      Certainly! Let's break down the provided code snippets:

      1. What is it and why is it used?

      In Mongoose, a schema is a blueprint for defining the structure of documents within a collection. When you define a schema, you can also attach methods to it. These methods become instance methods, meaning they are available on the individual documents (instances) created from that schema.

      Instance methods are useful for encapsulating functionality related to a specific document or model instance. They allow you to define custom behavior that can be executed on a specific document. In the given example, the findSimilarTypes method is added to instances of the Animal model, making it easy to find other animals of the same type.

      2. Syntax:

      Using methods object directly in the schema options:

      javascript const animalSchema = new Schema( { name: String, type: String }, { methods: { findSimilarTypes(cb) { return mongoose.model('Animal').find({ type: this.type }, cb); } } } );

      Using methods object directly in the schema:

      javascript animalSchema.methods.findSimilarTypes = function(cb) { return mongoose.model('Animal').find({ type: this.type }, cb); };

      Using Schema.method() helper:

      javascript animalSchema.method('findSimilarTypes', function(cb) { return mongoose.model('Animal').find({ type: this.type }, cb); });

      3. Explanation in Simple Words with Examples:

      Why it's Used:

      Imagine you have a collection of animals in your database, and you want to find other animals of the same type. Instead of writing the same logic repeatedly, you can define a method that can be called on each animal instance to find similar types. This helps in keeping your code DRY (Don't Repeat Yourself) and makes it easier to maintain.

      Example:

      ```javascript const mongoose = require('mongoose'); const { Schema } = mongoose;

      // Define a schema with a custom instance method const animalSchema = new Schema({ name: String, type: String });

      // Add a custom instance method to find similar types animalSchema.methods.findSimilarTypes = function(cb) { return mongoose.model('Animal').find({ type: this.type }, cb); };

      // Create the Animal model using the schema const Animal = mongoose.model('Animal', animalSchema);

      // Create an instance of Animal const dog = new Animal({ type: 'dog', name: 'Buddy' });

      // Use the custom method to find similar types dog.findSimilarTypes((err, similarAnimals) => { console.log(similarAnimals); }); ```

      In this example, findSimilarTypes is a custom instance method added to the Animal schema. When you create an instance of the Animal model (e.g., a dog), you can then call findSimilarTypes on that instance to find other animals with the same type. The method uses the this.type property, which refers to the type of the current animal instance. This allows you to easily reuse the logic for finding similar types across different instances of the Animal model.

      Certainly! Let's go through each part and explain it in simple terms: ### 1. `this` in Mongoose: - **What is `this`?** In JavaScript, `this` refers to the current context or object. In Mongoose, particularly within methods and middleware functions, `this` represents the instance (document) the function is currently operating on. - **Why is it used?** `this` is used to access and modify the properties of the current document. For example, in a Mongoose method, `this` allows you to refer to the fields of the specific document the method is called on. ### 2. Example: Let's use the `userSchema.pre("save", ...)`, which is a Mongoose middleware, as an example: ```javascript userSchema.pre("save", async function (next) { if (!this.isModified("password")) { next(); } else { this.password = await bcrypt.hash(this.password, 10); next(); } }); ``` - **Explanation in Simple Words:** - Imagine you have a system where users can sign up and set their password. - Before saving a new user to the database, you want to ensure that the password is securely encrypted (hashed) using a library like `bcrypt`. - The `userSchema.pre("save", ...)` is a special function that runs automatically before saving a user to the database. - In this function: - `this.isModified("password")`: Checks if the password field of the current user has been changed. - If the password is not modified, it means the user is not updating their password, so it just moves on to the next operation (saving the user). - If the password is modified, it means a new password is set or the existing one is changed. In this case, it uses `bcrypt.hash` to encrypt (hash) the password before saving it to the database. - The use of `this` here is crucial because it allows you to refer to the specific user document that's being saved. It ensures that the correct password is hashed for the current user being processed. In summary, `this` in Mongoose is a way to refer to the current document or instance, and it's commonly used to access and modify the properties of that document, especially in middleware functions like the one demonstrated here for password encryption before saving to the database.

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  2. Dec 2023
  3. Mar 2023
  4. Dec 2022
  5. Nov 2022
    1. by using symbols as keys, you will be able to use the implicit conversion of a Mash via the #to_hash method to destructure (or splat) the contents of a Mash out to a block

      This doesn't actually seem to be an example of destructure/splat. (When it said "destructure the contents ... out to a block", I was surprised and confused, because splatting is when you splat it into an argument or another hash — never a block.)

      An example of destructure/splat would be more like

      method_that_takes_kwargs(**symbol_mash)

  6. Jul 2022
  7. Jun 2022
  8. May 2022
    1. hash the source/destination IP:port tuples to the same worker thread.

      hash the source/destination IP:port tuples to the same worker thread.

    1. http://geohash.org/c216ne:Mt_Hood http://geohash.org/?q=45.37,-121.7&format=gpx http://geohash.org/?q=45.37,-121.7&format=url&redirect=0

      • osm — open the location in OpenStreetMaps
      • gmaps — open the location in Google Maps
      • gc — go to the nearest geocaches in Geocaching.com
      • gpx — go directly to GPX download page
      • garmin — go directly to Garmin download page
      • text — show coordinates as plain text
      • url — show Geohash URL as plain text
      • maxlen — maximum length of the Geohash
    1. hash://sha256/9f86d081884c7d659a2feaa0?type=text/plain#top \__/ \____/ \______________________/ \_____________/ \_/ | | | | | scheme algorithm hash query fragment

  9. Jan 2022
  10. Mar 2021
    1. A proposal to specify the path for bury with classes as values of a hash arg: {}.bury(users: Array, 0 => Hash, name: Hash, something: 'Value') # {user: [{name: {something: 'Value'}]} So all absent nodes could be created via klass.new

      Didn't understand it at first, but now I think it's a pretty clever/decent solution.

      Just a bit more verbose than one might like...

      At first I had reservations about the fact that this requires you to pass a hash ... or rather, once you start using a hash as your "list", you can't just "switch back" to an array (a "problem" I've noticed in RSpec, where you have some tags that are symbols, and some that are hashes: you have to list the symbols first: describe 'thing', :happy_path, driver: :chrome):

      {}.bury(users: Array, 0, 'Value')
      

      But I think that's okay in practice. Just use a hash for all "elements" in your list:

      {}.bury(users: Array, 0 => 'Value')
      
  11. Feb 2021
    1. The problem is that you what you want is actually not de-structuring at all. You’re trying to go from 'arg1', { hash2: 'bar', hash3: 'baz' }, { hash1: 'foo' } (remember that 'arg1', foo: 'bar' is just shorthand for 'arg1', { foo: 'bar' }) to 'arg1', { hash1: 'foo', hash2: 'bar', hash3: 'baz' } which is, by definition, merging (note how the surrounding structure—the hash—is still there). Whereas de-structuring goes from 'arg1', [1, 2, 3] to 'arg1', 1, 2, 3
    1. {a: 1, b: 2, c: 3, d: 4} => {a:, b:, **rest} # a == 1, b == 2, rest == {:c=>3, :d=>4}

      equivalent in javascript:

      {a, b, ...rest} = {a: 1, b: 2, c: 3, d: 4}
      

      Not a bad replacement for that! I still find javascript's syntax a little more easily readable and natural, but given that we can't use the same syntax (probably because it would be incompatible with existing syntax rules that we can't break for compatibility reasons, unfortunately), this is a pretty good compromise/solution that they've come up with.

  12. Oct 2020
  13. Jan 2020
  14. Oct 2018
    1. 8. Examples 8.1. Hello World! The following ni URI is generated from the text "Hello World!" (12 characters without the quotes), using the sha-256 algorithm shown with and without an authority field: ni:///sha-256;f4OxZX_x_FO5LcGBSKHWXfwtSx-j1ncoSt3SABJtkGk ni://example.com/sha-256;f4OxZX_x_FO5LcGBSKHWXfwtSx-j1ncoSt3SABJtkGk The following HTTP URL represents a mapping from the previous ni name based on the algorithm outlined above. http://example.com/.well-known/ni/sha-256/ f4OxZX_x_FO5LcGBSKHWXfwtSx-j1ncoSt3SABJtkGk
  15. Feb 2018
    1. imgHash.py

      具体实现:

      #!/usr/bin/python
      
      import glob
      import os
      import sys
      
      from PIL import Image
      
      EXTS = 'jpg', 'jpeg', 'JPG', 'JPEG', 'gif', 'GIF', 'png', 'PNG'
      
      def avhash(im):
          if not isinstance(im, Image.Image):
              im = Image.open(im)
          im = im.resize((8, 8), Image.ANTIALIAS).convert('L')
          avg = reduce(lambda x, y: x + y, im.getdata()) / 64.
          return reduce(lambda x, (y, z): x | (z << y),
                        enumerate(map(lambda i: 0 if i < avg else 1, im.getdata())),
                        0)
      
      def hamming(h1, h2):
          h, d = 0, h1 ^ h2
          while d:
              h += 1
              d &= d - 1
          return h
      
      if __name__ == '__main__':
          if len(sys.argv) <= 1 or len(sys.argv) > 3:
              print "Usage: %s image.jpg [dir]" % sys.argv[0]
          else:
              im, wd = sys.argv[1], '.' if len(sys.argv) < 3 else sys.argv[2]
              h = avhash(im)
      
              os.chdir(wd)
              images = []
              for ext in EXTS:
                  images.extend(glob.glob('*.%s' % ext))
      
              seq = []
              prog = int(len(images) > 50 and sys.stdout.isatty())
              for f in images:
                  seq.append((f, hamming(avhash(f), h)))
                  if prog:
                      perc = 100. * prog / len(images)
                      x = int(2 * perc / 5)
                      print '\rCalculating... [' + '#' * x + ' ' * (40 - x) + ']',
                      print '%.2f%%' % perc, '(%d/%d)' % (prog, len(images)),
                      sys.stdout.flush()
                      prog += 1
      
              if prog: print
              for f, ham in sorted(seq, key=lambda i: i[1]):
                  print "%d\t%s" % (ham, f)
      

      参考代码:

      1. http://www.ruanyifeng.com/blog/2011/07/imgHash.txt
  16. Sep 2017