Grails中的分页概率 [英] Pagination prob in Grails

问题描述

我想在分页中显示某个类别下的所有游戏(每页10个)这是我的控制器

I want to display all games under a certain category in pagination (10/page) This is my controller

def listGame(){
    def category = GameCategory.list()
    def platform = Platform.list()
    def currentCategory = params.categoryName
    def myCategory=GameCategory.findByCategoryName(currentCategory)
    def games = myCategory.games

    [currentCategory:currentCategory, category:category, games:games,  platforms:platform, gameCount:Game.count(), chosenPlatform:params.platform] 
}

这是我看来的分页代码

<g:each in="${games}" status="i" var="game">
    ${game.gameTitle}
</g:each>
<div class="pagination">
            <g:paginate action="listGame" total="${gameCount}" />
</div>

当我在当前类别中有9场比赛时，第12页出现了，不应出现

When I have 9 games in the current category the page 12 showed up wherein it shouldn't

当我当前类别中有11个游戏时，所有11个游戏都显示在第1页中，而单击第2页将导致此错误

When I have 11 games in the current category all 11 games are displayed in page 1 and clicking page 2 will result in this error

推荐答案

有几件事要解决.

1. 确保 categoryName 不会以 null 的形式进入控制器.
2. 利用分页器提供的 max 和 offset 参数来选择适当的 Game .

1. Make sure categoryName is not coming into the controller as null.
2. Make use of the max and offset parameters that the paginator is providing to select the appropriate Games.

类别名称

由于分页器正在创建调用控制器的URL，并且您的控制器需要类别名称，因此分页器必须将类别名称添加到调用控制器操作的参数中.您可以使用代码的 params 属性

<g:paginate action="listGame" total="${gameCount}" params="${[categoryName: currentCategory]}"/>

Max&偏移量

控制器需要使用 max 和 offset 参数来了解要从数据库中检索 Game 的哪些子集并在数据库中呈现看法.但是，在某些情况下，例如访问URL http://blah/someController/listGame 时，没有 max 和 offset 参数.这是您的控制器动作必须能够处理的.它是这样的:

Max & offset

The controller needs to use max and offset parameters to know what subset of the Games to retrieve from the database and render in the view. However, in some cases, such as when visiting the URL http://blah/someController/listGame, there would be no max and offset params. This is something your controller action must be able to handle. It goes something like this:

def max = params.max ?: 10
def offset = params.offset ?: 0

因此，将使用 max 和 offset 参数(如果可用).否则，它们将使用默认值.

So the max and offset params will be used if they are available. Otherwise they'll use default values.

最后，您需要使用这些参数来选择 Game .为此，您可以使用 where 查询:

Finally, you need to use these parameters to select the Games. For that you can use a where query:

def games = Game.where {
    categories.categoryName == currentCategory
}.list(max: max, offset: offset)

关于返回的 games 对象的一些有趣的事情:它像一个列表，但实际上是一个 grails.gorm.PagedResultList .这是一件好事，因为它在结果中包含记录的 total 总数(忽略max和offset).换句话说，这就是您的新 gameCount .

Something interesting about the returned games object: It acts like a list, but it's actually a grails.gorm.PagedResultList. That's a good thing because it contains the total number of records in the result (ignoring max and offset). In other words, it's your new gameCount.

您可以在中阅读有关 where 查询的更多信息.Grails文档.我也有一系列的文章，其中涵盖了位置，条件和HQL查询更详细.

You can read more about where queries in the Grails documentation. I also have a series of articles which cover where, criteria and HQL queries in more detail.

将所有内容放在一起， listGame()看起来像这样:

Putting it all together, listGame() would look like this:

def listGame(){
    def category = GameCategory.list()
    def platform = Platform.list()
    def currentCategory = params.categoryName
    def max = params.max ?: 10
    def offset = params.offset ?: 0
    def games = Game.where {
        categories.categoryName == currentCategory
    }.list(max: max, offset: offset)

    [currentCategory:currentCategory, category:category, games:games,  platforms:platform, gameCount:games.totalCount, chosenPlatform:params.platform] 
}

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