default-value

问题 I have the following architecture: architecture datapath of DE2_TOP is begin U1: entity work.lab1 port map ( --error on this line clock => clock_50, key => key, hex6 => hex6, hex5 => hex5, hex4 => hex4 ); end datapath; This architecture obviously depends on lab1 entity. Here is my lab1 entity and architecture: entity lab1 is port( clock : in std_logic; key : in std_logic_vector(3 downto 0); hex4, hex5, hex6 : out std_logic_vector(6 downto 0); value_counter : in unsigned(7 downto 0); register

问题 I'm using preferences.xml to allow selection of a ringtone (among other preferences). Here's the code <RingtonePreference android:key="shuttle_tone" android:ringtoneType="notification" android:showDefault="false" android:showSilent="true" android:defaultValue="content://settings/system/notification_sound" android:summary="Select the tone that signals the start of the next shuttle" android:title="Shuttle Tone" /> ... a bunch of other preferences The Preferences activity is initiated in the

问题 I've got an object that is being serialized / deserialized via the XmlSerializer in C#, .NET 3.5. One of the properties (and more in the future) is a collection: List where T is an enum value. This serializes / deserializes fine. We are also using a "default values" mechanism to provide default values for the object, in case the serialized version doesn't have any value set. as a simple example, here is what we are dong: public enum MyEnum { Value1, Value2 } public class Foo { public List

问题 This question already has answers here : Strange, unexpected behavior (disappearing/changing values) when using Hash default value, e.g. Hash.new([]) (4 answers) Closed 4 years ago . Today I tried the following snippets of code and I don't understand why I get different results between them. As far as I can understand they are the same. One uses the default value off Hash and the other snippet creates an empty array for the key before it'll be accessed. Anyone who understands what's going on?

问题 I've a table with 52 columns in my database and I want to write a function to create a row in that table. In my case, I don't want to use all columns in that table, so I created my model like this. [Table("CUST_MASTER")] public class CustomerMaster { [Key] [Column("CUSTOMER_ID")] public string Id { get; set; } [Column("CUSTOMER_NAME")] public string Name { get; set; } [Column("CUSTOMER_CITY")] public string City { get; set; } } Is there any way to send only this data via Entity framework and

问题 models.py class Aref5(models.Model): name = Aref5.objects.all.order_by('id')[0] Rthink = models.TextField(max_length=2000, blank=True, default=name) <....> I would like to have the default value of Rthink be the id of the the last item. With the above code I get an error saying that Aref5 is not recognized. How can I access existing Aref5 instances within the definition of Aref5 ? 回答1: There are a couple of problems here. One is that if this were to work, name would be computed once whenever

问题 I have a decimal field in my MySQL database. I have defined it as this: decimal(1,1) UNSIGNED NULL . But I would like to set a default value for it like 7.0 , and this is the problem I have. Whenever I want to set this value, I get this error: Invalid default value ... I also tried to set it as 7,0 and 7 but it resulted the same error. What is the correct default value for a MySQL decimal field? Note: I am using Navicat for MySQL 回答1: In MySQL, when declaring DECIMAL(P,S) : The precision (P)

问题 I want to define a resize(h, w) method, and I want to be able to call it in one of two ways: resize(x,y) resize(x) Where, in the second call, I want y to be equal to x . Can I do this in the method definition or should I do something like resize(x,y=None) and check inside: if y is None: y = x 回答1: Can I do this in the method definition No. During the method definition there's no way to know what value x might have at run-time. Default arguments are evaluated once at definition time, there's

问题 I've worked with WCF for awhile now and in places where both client and server tend to be co-released; that is, new versions have almost always been released at the same time. Interoperability and versioning aren't issues (in this case at least). The MSDN documentation, DataMemberAttribute.EmitDefaultValue and Data Contract Versioning, suggests it is a bad practice to emit the default value unless there is a specific need and to support versioning. In practice, I've found it useful and at

问题 Let's say I have the following struct: struct myStruct { int x; int y; int z; int w; }; I want to initialize this struct to a default value when calling the following function. If it helps I'm looking for a simple zero initialization. void myFunc(myStruct param={0,0,0,0}) { ... } This code however gives me compile error. I've tried VS2003 and VS2008. NOTE: I have looked at other answers mentioning the use of constructor. However I want the user to see what values I'm using for initialization.