readonly | 易学教程

Read/Write Python Closures

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Closures are an incredibly useful language feature. They let us do clever things that would otherwise take a lot of code, and often enable us to write code that is more elegant and more clear. In Python 2.x, closures variable names cannot be rebound; that is, a function defined inside another lexical scope cannot do something like some_var = 'changed!' for variables outside of its local scope. Can someone explain why that is? There have been situations in which I would like to create a closure that rebinds variables in the outer scope, but it wasn't possible. I realize that in almost all cases

How can I enable jquery validation on readonly fields?

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问题 Guys from http://jqueryvalidation.org/ just released version 1.13.1. Checking on their website i see this on the changelog: CORE: * Ignore readonly as well as disabled fields. (9f4ba10) This is the link: https://github.com/jzaefferer/jquery-validation/commit/9f4ba10ea79b4cf59225468d6ec29911f0e53a0a I use some bootstrap templates and one of them now uses that version. That brings me a problem, i use readonly attribute to prevent users typing dates manually, so their only option is to choose a

Why Tuple's items are ReadOnly?

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问题 I was thinking to use Tuple class to store 2 integer information (StartAddress, EndAddress) I need in my program. But I discover that Tuple items are ReadOnly, so if I need to set a value for an item, I need to re-instantiate a Tuple. What is the reason behind this design decision? 回答1: Tuples originated in functional programming. In (purely) functional programming, everything is immutable by design - a certain variable only has a single definition at all times, as in mathematics. The .NET

Python read-only property

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问题 I don\'t know when attribute should be private and if I should use property. I read recently that setters and getters are not pythonic and I should use property decorator. It\'s ok. But what if I have attribute, that mustn\'t be set from outside of class but can be read (read-only attribute). Should this attribute be private, and by private I mean with underscore, like that self._x ? If yes then how can I read it without using getter? Only method I know right now is to write @property def x

Why can't radio buttons be “readonly”?

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问题 I would like to show a radio button, have its value submitted, but depending on the circumstances, have it not editable. Disabled doesn\'t work, because it doesn\'t submit the value (or does it?), and it grays out the radio button. Read-only is really what I\'m looking for, but for some mysterious reason it doesn\'t work. Is there some weird trick I need to pull to get read-only to work as expected? Should I just do it in JavaScript instead? Incidentally, does anyone know why read-only doesn\

How to make Entity Framework Data Context Readonly

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问题 I need to expose an Entity Framework Data Context to 3rd party plugins. The purpose is to allow these plugins to fetch data only and not to let them issue inserts, updates or deletes or any other database modification commands. Hence how can I make a data context or entity readonly. 回答1: In addition to connecting with a read-only user, there are a few other things you can do to your DbContext. public class MyReadOnlyContext : DbContext { // Use ReadOnlyConnectionString from App/Web.config

Java / Hibernate - Write operations are not allowed in read-only mode

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问题 I\'ve been having an annoying exception a lot lately, and after some research on Google and this forum I still haven\'t found an answer that could solve my problem. Here\'s the thing - sometimes, I get the following error when trying to update or create a new object with hibernate: org.springframework.dao.InvalidDataAccessApiUsageException: Write operations are not allowed in read-only mode (FlushMode.NEVER/MANUAL): Turn your Session into FlushMode.COMMIT/AUTO or remove \'readOnly\' marker

Why does C# disallow readonly local variables?

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问题 Having a friendly debate with a co-worker about this. We have some thoughts about this, but wondering what the SO crowd thinks about this? 回答1: One reason is there is no CLR support for a readonly local. Readonly is translated into the CLR/CLI initonly opcode. This flag can only be applied to fields and has no meaning for a local. In fact, applying it to a local will likely produce unverifiable code. This doesn't mean that C# couldn't do this. But it would give two different meanings to the

How to implement a read only property

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问题 I need to implement a read only property on my type. Moreover the value of this property is going to be set in the constructor and it is not going to be changed (I am writing a class that exposes custom routed UI commands for WPF but it does not matter). I see two ways to do it: class MyClass { public readonly object MyProperty = new object(); } class MyClass { private readonly object my_property = new object(); public object MyProperty { get { return my_property; } } } With all these FxCop

Is there a read-only generic dictionary available in .NET?

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I'm returning a reference to a dictionary in my read only property. How do I prevent consumers from changing my data? If this were an IList I could simply return it AsReadOnly . Is there something similar I can do with a dictionary? Private _mydictionary As Dictionary(Of String, String) Public ReadOnly Property MyDictionary() As Dictionary(Of String, String) Get Return _mydictionary End Get End Property Thomas Levesque Here's a simple implementation that wraps a dictionary: public class ReadOnlyDictionary<TKey, TValue> : IDictionary<TKey, TValue> { private readonly IDictionary<TKey, TValue>