Creating custom widgets

which is how we're able to use our reusable card … to style each of them, … and have them laid out using our expanded widgets, … but their content are all different. … And usually in Flutter, … when we're using the widgets that Flutter have created, … they tend to address this by having a child property. … because we're getting an error that tells us, … the final variable cardChild must be initialized, … so we do that in here. … Now, I don't think the child property should be required, … so we don't need to add the required annotation. … All we need to do is just write this.cardChild. … So that means if we create a new reusable card, … then we can if we wish to add a child … to go inside our widget. … But if we don't need to have any content, … then we can just simply have it as is. … Now the final thing is, … where is this child going to be placed inside our widget tree? … Well, it's going to be a child of our container. … So we're going to tap into the container's child property, … and we're going to say that whatever cardChild …