subclass

Can't figure out ActiveRecord::SubclassNotFound in Registries#edit?

由 你说的曾经没有我的故事 提交于 2019-12-02 07:08:38
When in "edit" or "show" this comes up: ActiveRecord::SubclassNotFound in Registries#edit "The single-table inheritance mechanism failed to locate the subclass: 'Plane'. This error is raised because the column 'type' is reserved for storing the class in case of inheritance. Please rename this column if you didn't intend it to be used for storing the inheritance class or overwrite Present.inheritance_column to use another column for that information." 25: </div> 26: 27: <div class="field1"> 28: <%= f.fields_for :presents do |builder| %> 29: <%= render 'present_fields', f: builder %> 30: <% end

why we can't override a method and define it to return a superclass of the original method?

由 大兔子大兔子 提交于 2019-12-02 06:09:33
问题 I'm currently learning Java classes and objects from java tutorial oracle and have encountered the following statements and code. I understand the concept but I do not know why we can't override a method and define it to return a superclass of the original method? What is the reason behind it? Could someone please enlighten me? Thanks in advance for any help! You can override a method and define it to return a subclass of the original method, like this: public Number returnANumber() { ... }

Subclassing an NSTextField

由 家住魔仙堡 提交于 2019-12-02 05:32:23
问题 Given all the complex things I seem to cover every day, this appears to be a "what the heck am I doing wrong that seems to simple?" scenario! I would like to subclass an NSTextField to change the background color and text color. For simplicity sake (and to help anyone who hasn't ever subclassed anything before), here is the example of my (simplified) subclass MyNSTextFieldSubclass ... Step 1: Create the subclass file: First the header file @interface MyTextFieldSubclass : NSTextField { } @end

Declare all instances of a typeclass are in another typeclass without modifying the original class declarations

由 喜欢而已 提交于 2019-12-02 04:46:07
There is an Crypto.Random API inside the crypto-api package that specifies what it means for something to be a "pseudorandom number generator". I have implemented this API using an instance of System.Random's RandomGen class, namely, StdGen: instance CryptoRandomGen StdGen where newGen bs = Right $ mkStdGen $ shift e1 24 + shift e2 16 + shift e3 8 + e4 where (e1 : e2 : e3 : e4 : _) = Prelude.map fromIntegral $ unpack bs genSeedLength = Tagged 4 genBytes n g = Right $ genBytesHelper n empty g where genBytesHelper 0 partial gen = (partial, gen) genBytesHelper n partial gen = genBytesHelper (n-1)

Have a databound WPF Listbox generate subclassed ListboxItems

由 对着背影说爱祢 提交于 2019-12-02 04:35:40
问题 I would like to have my WPF Listbox, which is databound, generate subclassed ListboxItems instead of the regular ListboxItems. In this case, a DataTemplate is not sufficient because I need some custom properties for the subclassed ListBoxItems. Is there a way to have the ListBox generated mySubClassedListBoxItem items for the bound data? Thanks, Bart 回答1: You need to create your own subclass of ListBox so you can override the method which creates the container, e.g. public class MyListBox :

Have a databound WPF Listbox generate subclassed ListboxItems

由 大兔子大兔子 提交于 2019-12-02 00:04:55
I would like to have my WPF Listbox, which is databound, generate subclassed ListboxItems instead of the regular ListboxItems. In this case, a DataTemplate is not sufficient because I need some custom properties for the subclassed ListBoxItems. Is there a way to have the ListBox generated mySubClassedListBoxItem items for the bound data? Thanks, Bart You need to create your own subclass of ListBox so you can override the method which creates the container, e.g. public class MyListBox : ListBox { public MyListBox() { // Should get the default style & template since styles are not inherited

Can't subclass UIColor?

由 元气小坏坏 提交于 2019-12-01 23:15:25
I'm trying to subclass UIColor, and I can't seem to figure out what's wrong. In my PColor.h #import <Foundation/Foundation.h> @interface PColor : UIColor { BOOL isAvailable; int colorId; } @property (nonatomic, assign) BOOL isAvailable; @property (nonatomic, assign) int colorId; @end ...and in my PColor.m #import "PColor.h" @implementation PColor @synthesize isAvailable; @synthesize colorId; @end Upon instantiating a PColor object, I get: //warning: incompatible Objective-C types initializing 'struct UIColor *', expected 'struct PColor *' PColor *pcolor = [[PColor alloc] initWithHue:1

subclassed python dictionary for custom namespace in exec() method

由 泪湿孤枕 提交于 2019-12-01 23:12:52
I am trying to subclass a dictionary for use in an exec method. Ultimately, I would like the local function to have a custom name scoping behaviour. In the code below, function b() does in fact have the correct globals() dictionary available to it, however it fails to search it when resolving z . Does function b() first not search locals() then globals() ? Very puzzling. Any help appreciated. t = ''' def b(): # return (globals()['z']) #works return z #fails b() ''' class MyDict(dict): def __init__(self, g): dict.__init__(self) self.my_g = g def __getitem__(self, key): print("GET ", key) try:

Can't subclass UIColor?

由 做~自己de王妃 提交于 2019-12-01 22:57:37
问题 I'm trying to subclass UIColor, and I can't seem to figure out what's wrong. In my PColor.h #import <Foundation/Foundation.h> @interface PColor : UIColor { BOOL isAvailable; int colorId; } @property (nonatomic, assign) BOOL isAvailable; @property (nonatomic, assign) int colorId; @end ...and in my PColor.m #import "PColor.h" @implementation PColor @synthesize isAvailable; @synthesize colorId; @end Upon instantiating a PColor object, I get: //warning: incompatible Objective-C types initializing

instanceof check works on subclass without setting constructor [duplicate]

由 空扰寡人 提交于 2019-12-01 20:46:07
问题 This question already has answers here : What's the difference between using instanceof and checking the constructor? (2 answers) Closed 3 years ago . I have the following JavaScript code function Parent() { } function Child() { } Child.prototype = Object.create(Parent.prototype); Note the absence of the statement Child.prototype.constructor = Child; My understanding is that as the constructor property has not been set the instanceof checks should fail for new instances of Child class. var
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