readonly

问题 In C#, I have some static data that could be put in a Dictionary<int, T> where T is some reference type. The web app only needs to initialize it once, statically (it doesn't change). Since I don't have to worried about insert or delete performance, what is the best data structure to use (or should I roll my own)? I'm probably looking at something like ~100,000 entries, fairly evenly spaced. I am looking for an optimal algorithm for fetching this data. Dictionary<> isn't bad, but I would

问题 I am using setReadOnly method to make my app's directory stored on my SD card 'Read-only'. However this method when called is returning 'false' even though I have provided the app with android.permission.WRITE_EXTERNAL_STORAGE permission in the manifest. Here's my code : is.close(); fos.close(); Decompress d = new Decompress(productDirectory + "/downloadedfile.zip", productDirectory + "/unzipped/"); d.unzip(); File zipfile = new File(productDirectory + "/downloadedfile.zip"); zipfile.delete()

问题 I am using web2py forms and i want to have some fields only visible to user (as fixed which cannot be edited). I tried making various combinations of editable, writeable, readonly but was of no use. I looked into web2py book too but that also seems insufficient. It would be great if someone can tell me how to do this. 回答1: You mean some fields visible to all visitors and some fields visible only if logged in? If that's the case, then build your form conditionally: form_fields = [ Field(

问题 Every so often, I'm done modifying a piece of code and I would like to "lock" or make a region of code "read only". That way, the only way I can modify the code is if I unlock it first. Is there any way to do this? 回答1: The easiest way which would work in many cases is to make it a partial type - i.e. a single class whose source code is spread across multiple files. You could then make one file read-only and the other writable. To declare a partial type, you just use the partial contextual

问题 Is it possible to get a value from a collection and apply a method to it which accepts only self and not &self ? Minimal Working Example What I would like to write is something akin to: use std::collections::HashMap; fn get<B>(key: i32, h: HashMap<i32, Vec<(i32, B)>>) -> i32 where B: Into<i32> { let v: &Vec<(i32, B)> = h.get(&key).unwrap(); let val: &B = v.first().unwrap().1; // Do something to be able to call into // I only need the value as read-only // Does B have to implement the Clone

问题 Currently I use Entity Framework code first to create my domain models. As the code below illustrates, I want create a one-to-many association between "Test2" class and "Test1" class. But when I ran the application, it threw an exception: The navigation property 'T2' is not a declared property on type 'Test1'. Verify that it has not been explicitly excluded from the model and that it is a valid navigation property. If I modify the navigation property "T2" to make it have a "protected" or

问题 I know hibernate but I wonder if there would be a lighter ORM engine for a read only database. I mean, I don't need some transactional queries or to update some records. On the other side, I need to handle some large list of records: List<MyRecord> list= object.getMyRecords(); // list.size() > 1E7 Does such engine exist ? Many thanks, Pierre 回答1: You can check out JIRM (yes, that is a shameless plug) which is an ORM focused on using immutable objects. It sits right on top of Spring JDBC so,

问题 I don't know if this is possible but I would like to have an input field where I would have a value that is not editable by the user. However, I don't want the input field to be "readonly" because I still want the user to be able to add text after the value. If you have any idea on how to do this, let me know please that would help me a lot. EDIT: I use html forms. 回答1: You can position the text on top of the input field to make it look as if it is inside it. Something like this: <input type=

问题 C# compiler gave me the following error CS0191: A readonly field cannot be assigned to (except in a constructor or a variable initializer) Do I have to move the code (in my private function) into the constructor? That sounds awkward. Note that the private method was intended only to be called by the constructor. I expect that there is some sort of attribute that I can use to mark the method corresponding. 回答1: Despite what the other posts are saying, there is actually a (somewhat unusual) way

问题 I wonder why it is not possible to do the following: struct TestStruct { public readonly object TestField; } TestStruct ts = new TestStruct { /* TestField = "something" // Impossible */ }; Shouldn't the object initializer be able to set the value of the fields ? 回答1: Object Initializer internally uses a temporary object and then assign each value to the properties. Having a readonly field would break that. Following TestStruct ts = new TestStruct { TestField = "something"; }; Would translate