Access Custom Object Property While Iterating Over Dictionary

Access custom object property while iterating over dictionary

you are iterating over a dictionary by looking at it keys and values.

But the values aren't strings but arrays of strings.

do

import Foundation

struct object {
    var title:String?
}

var one = object(title:"green")
var two = object(title:"black")
var three = object(title:"blue")

var dict = ["a":[one, two], "b":[three]]

for (key, value) in dict {
    for obj in value {
        if let title = obj.title {
            if title.lowercaseString.containsString(searchText.lowercaseString) {
                // ...
            }
        }
    }

}

iterate custom dictionary object

You can iterate over either the keys or the items of a dictionary:

Sub Tester()

Dim d As New Scripting.Dictionary
Dim k

    d.Add "one", 1
    d.Add "two", 2
    d.Add "three", 3

    For Each k In d.Keys
        Debug.Print k
    Next

    For Each k In d.Items
        Debug.Print k
    Next

End Sub 

So, you can expose your dictionary as a property of an object and iterate over that. It does mean you need to specify .Items though (since it will default to keys.

How to iterate over a JavaScript object?

For iterating on keys of Arrays, Strings, or Objects, use for .. in :

for (let key in yourobject) {
  console.log(key, yourobject[key]);
}

With ES6, if you need both keys and values simultaneously, do

for (let [key, value] of Object.entries(yourobject)) {
    console.log(key, value);
}

To avoid logging inherited properties, check with hasOwnProperty :

for (let key in yourobject) {
   if (yourobject.hasOwnProperty(key)) {
      console.log(key, yourobject[key]);
   }
}

You don't need to check hasOwnProperty when iterating on keys if you're using a simple object (for example one you made yourself with {}).

This MDN documentation explains more generally how to deal with objects and their properties.

If you want to do it "in chunks", the best is to extract the keys in an array. As the order isn't guaranteed, this is the proper way. In modern browsers, you can use

let keys = Object.keys(yourobject);

To be more compatible, you'd better do this :

 let keys = [];
 for (let key in yourobject) {      
     if (yourobject.hasOwnProperty(key)) keys.push(key);
 }

Then you can iterate on your properties by index: yourobject[keys[i]] :

for (let i=300; i < keys.length && i < 600; i++) { 
   console.log(keys[i], yourobject[keys[i]]);
}

How to iterate over `dict` in class like if just referring to `dict`?

You'll have to implement the .keys(), .values() and .items() methods yourself; together with __iter__ they can all delegate the actual work to the self.values() dictionary:

class Klass:
    def __init__(self, values):
        self._values = values
        self.more = None

    def __getitem__(self, name):
        return self._values[name]

    def __iter__(self):
        return iter(self._values)

    def keys(self):
        return self._values.keys()

    def items(self):
        return self._values.items()

    def values(self):
        return self._values.values()

I renamed the attribute to avoid masking the .values() method.

The easiest way to delegate __iter__ to iteration over the dictionary (by key) is to use the iter() function to get an iterator for the dictionary object.

To be explicit: __iter__ plays no role in how .keys(), .values() and .items() are handled; the latter are just more methods.

Iterate over object attributes in python

Assuming you have a class such as

>>> class Cls(object):
...     foo = 1
...     bar = 'hello'
...     def func(self):
...         return 'call me'
...
>>> obj = Cls()

calling dir on the object gives you back all the attributes of that object, including python special attributes. Although some object attributes are callable, such as methods.

>>> dir(obj)
['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'bar', 'foo', 'func']

You can always filter out the special methods by using a list comprehension.

>>> [a for a in dir(obj) if not a.startswith('__')]
['bar', 'foo', 'func']

or if you prefer map/filters.

>>> filter(lambda a: not a.startswith('__'), dir(obj))
['bar', 'foo', 'func']

If you want to filter out the methods, you can use the builtin callable as a check.

>>> [a for a in dir(obj) if not a.startswith('__') and not callable(getattr(obj, a))]
['bar', 'foo']

You could also inspect the difference between your class and its instance object using.

>>> set(dir(Cls)) - set(dir(object))
set(['__module__', 'bar', 'func', '__dict__', 'foo', '__weakref__'])

Custom iterator for dictionary?

In C#3 and above you can use a (LINQ) extension method:

var myFilteredCollection = myCollection.Where( x => x.AmIIncludedInTheIteration );

foreach (var x in myFilteredCollection ) ...

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