WeChat small program cloud development API update instructions

db.command.set

Update the instruction. Used to set the field equal to the specified value.

Function signature:

function set(value: any): Command

The advantage of this approach over passing in pure JS objects is the ability to specify that a field is equal to one object:

// 以下方法只会更新 style.color 为 red，而不是将 style 更新为 { color: 'red' }，即不影响 style 中的其他字段
db.collection('todos').doc('doc-id').update({
  data: {
    style: {
      color: 'red'
    }
  }
})

// 以下方法更新 style 为 { color: 'red', size: 'large' }
db.collection('todos').doc('doc-id').update({
  data: {
    style: _.set({
      color: 'red',
      size: 'large'
    })
  }
})

---

db.command.remove

Update the instruction. Used to indicate the deletion of a field.

Function signature:

function remove(): Command

The sample code

Remove the style field:

const _ = db.command
db.collection('todos').doc('todo-id').update({
  data: {
    style: _.remove()
  }
})

---

db.command.inc

Update the instruction. Used to indicate that the field adds a value, which is an atomic operation, and the advantage of using this instruction instead of reading the data first, then adding it, and then writing it back is:

1. Atomicity: Multiple users write at the same time, for the database is to add fields to one, there will be no later override of the former situation
2. Reduce a network request: you don't need to read and write

The mul directive is the same.

Function signature:

function inc(value: number): Command

The sample code

Increase the progress of a todo by 10:

const _ = db.command
db.collection('todos').doc('todo-id').update({
  data: {
    progress: _.inc(10)
  }
})

---

db.command.mul

Update the instruction. Used to indicate that a field multiplies a value, which is an atomic operation, and the advantage of using this instruction instead of reading the data first, then adding, and then writing it back is:

1. Atomicity: Multiple users write at the same time, for the database are self-multiplied fields, there will be no later override of the former situation
2. Reduce a network request: you don't need to read and write

The inc directive is the same.

Function signature:

function mul(value: number): Command

The sample code

Multiply the progress of a todo by 2:

const _ = db.command
db.collection('todos').doc('todo-id').update({
  data: {
    progress: _.mul(2)
  }
})

---

db.command.push

Update the instruction to add one or more values to the end of the array to a field with an array of values. Or if the field was originally empty, the field is created and an array is set as an incoming value.

Function signature:

function push(values: any[]): Command

The sample code

const _ = db.command
db.collection('todos').doc('doc-id').update({
  data: {
    tags: _.push(['mini-program', 'cloud'])
  }
})

---

db.command.pop

Update the instruction to remove the tail element of the array from a field with an array value.

Function signature:

function pop(values: any[]): Command

The sample code

const _ = db.command
db.collection('todos').doc('doc-id').update({
  data: {
    tags: _.pop()
  }
})

---

db.command.shift

Update the instruction to remove the array header element from a field with an array value.

Function signature:

function shift(values: any[]): Command

The sample code

const _ = db.command
db.collection('todos').doc('doc-id').update({
  data: {
    tags: _.shift()
  }
})

---

db.command.unshift

Update the instruction to add one or more values to the head of the array to a field with an array value. Or if the field was originally empty, the field is created and an array is set as an incoming value.

Function signature:

function unshift(values: any[]): Command

The sample code

const _ = db.command
db.collection('todos').doc('doc-id').update({
  data: {
    tags: _.unshift(['mini-program', 'cloud'])
  }
})